diff --git a/config/config.md b/config/config.md
index f28d09e28d..fb683eaaea 100644
--- a/config/config.md
+++ b/config/config.md
@@ -139,7 +139,7 @@
 | `region_engine.mito.max_background_flushes` | Integer | Auto | Max number of running background flush jobs (default: 1/2 of cpu cores). |
 | `region_engine.mito.max_background_compactions` | Integer | Auto | Max number of running background compaction jobs (default: 1/4 of cpu cores). |
 | `region_engine.mito.max_background_purges` | Integer | Auto | Max number of running background purge jobs (default: number of cpu cores). |
-| `region_engine.mito.experimental_compaction_memory_limit` | String | 0 | Memory budget for compaction tasks. Setting it to 0 or "unlimited" disables the limit. |
+| `region_engine.mito.experimental_compaction_memory_limit` | String | 0 | Memory budget for compaction tasks.<br/>Supports absolute size (e.g., "2GiB", "512MB") or percentage of system memory (e.g., "50%").<br/>Setting it to 0 or "unlimited" disables the limit. |
 | `region_engine.mito.experimental_compaction_on_exhausted` | String | wait | Behavior when compaction cannot acquire memory from the budget.<br/>Options: "wait" (default, 10s), "wait(<duration>)", "fail" |
 | `region_engine.mito.auto_flush_interval` | String | `1h` | Interval to auto flush a region if it has not flushed yet. |
 | `region_engine.mito.global_write_buffer_size` | String | Auto | Global write buffer size for all regions. If not set, it's default to 1/8 of OS memory with a max limitation of 1GB. |
@@ -531,7 +531,7 @@
 | `region_engine.mito.max_background_flushes` | Integer | Auto | Max number of running background flush jobs (default: 1/2 of cpu cores). |
 | `region_engine.mito.max_background_compactions` | Integer | Auto | Max number of running background compaction jobs (default: 1/4 of cpu cores). |
 | `region_engine.mito.max_background_purges` | Integer | Auto | Max number of running background purge jobs (default: number of cpu cores). |
-| `region_engine.mito.experimental_compaction_memory_limit` | String | 0 | Memory budget for compaction tasks. Setting it to 0 or "unlimited" disables the limit. |
+| `region_engine.mito.experimental_compaction_memory_limit` | String | 0 | Memory budget for compaction tasks.<br/>Supports absolute size (e.g., "2GiB", "512MB") or percentage of system memory (e.g., "50%").<br/>Setting it to 0 or "unlimited" disables the limit. |
 | `region_engine.mito.experimental_compaction_on_exhausted` | String | wait | Behavior when compaction cannot acquire memory from the budget.<br/>Options: "wait" (default, 10s), "wait(<duration>)", "fail" |
 | `region_engine.mito.auto_flush_interval` | String | `1h` | Interval to auto flush a region if it has not flushed yet. |
 | `region_engine.mito.global_write_buffer_size` | String | Auto | Global write buffer size for all regions. If not set, it's default to 1/8 of OS memory with a max limitation of 1GB. |
diff --git a/config/datanode.example.toml b/config/datanode.example.toml
index 10e6965b84..6effec4c87 100644
--- a/config/datanode.example.toml
+++ b/config/datanode.example.toml
@@ -446,7 +446,9 @@ compress_manifest = false
 ## @toml2docs:none-default="Auto"
 #+ max_background_purges = 8
 
-## Memory budget for compaction tasks. Setting it to 0 or "unlimited" disables the limit.
+## Memory budget for compaction tasks.
+## Supports absolute size (e.g., "2GiB", "512MB") or percentage of system memory (e.g., "50%").
+## Setting it to 0 or "unlimited" disables the limit.
 ## @toml2docs:none-default="0"
 #+ experimental_compaction_memory_limit = "0"
 
diff --git a/config/standalone.example.toml b/config/standalone.example.toml
index 486bc74af2..7c7faa8a8b 100644
--- a/config/standalone.example.toml
+++ b/config/standalone.example.toml
@@ -538,7 +538,9 @@ compress_manifest = false
 ## @toml2docs:none-default="Auto"
 #+ max_background_purges = 8
 
-## Memory budget for compaction tasks. Setting it to 0 or "unlimited" disables the limit.
+## Memory budget for compaction tasks.
+## Supports absolute size (e.g., "2GiB", "512MB") or percentage of system memory (e.g., "50%").
+## Setting it to 0 or "unlimited" disables the limit.
 ## @toml2docs:none-default="0"
 #+ experimental_compaction_memory_limit = "0"
 
diff --git a/src/mito2/src/config.rs b/src/mito2/src/config.rs
index b3ddb023cb..120b5adbe3 100644
--- a/src/mito2/src/config.rs
+++ b/src/mito2/src/config.rs
@@ -91,7 +91,9 @@ pub struct MitoConfig {
     pub max_background_compactions: usize,
     /// Max number of running background purge jobs (default: number of cpu cores).
     pub max_background_purges: usize,
-    /// Memory budget for compaction tasks. Setting it to 0 or "unlimited" disables the limit.
+    /// Memory budget for compaction tasks.
+    /// Supports absolute size (e.g., "2GiB", "512MB") or percentage of system memory (e.g., "50%").
+    /// Setting it to 0 or "unlimited" disables the limit.
     pub experimental_compaction_memory_limit: MemoryLimit,
     /// Behavior when compaction cannot acquire memory from the budget.
     pub experimental_compaction_on_exhausted: OnExhaustedPolicy,