diff --git a/docs_new/docs/advanced_features/pd_disaggregation.mdx b/docs_new/docs/advanced_features/pd_disaggregation.mdx
index ff92b55db..dc0ef981b 100644
--- a/docs_new/docs/advanced_features/pd_disaggregation.mdx
+++ b/docs_new/docs/advanced_features/pd_disaggregation.mdx
@@ -36,6 +36,16 @@ For deploying PD disaggregation at scale with load balancing and fault tolerance
 uv pip install mooncake-transfer-engine
 ```
 
+### IB Device Configuration
+
+`--disaggregation-ib-device` supports the following formats when using the Mooncake backend:
+
+1. Shared device list for all GPUs: `mlx5_0` or `mlx5_0,mlx5_1`
+2. Per-GPU JSON mapping: `{"0": "mlx5_0,mlx5_1", "1": "mlx5_2,mlx5_3"}`
+3. Path to a JSON file containing the same per-GPU mapping
+
+Each JSON value uses the same comma-separated device list format as the shared configuration.
+
 ### Usage
 
 ### Llama Single Node
diff --git a/python/sglang/srt/server_args.py b/python/sglang/srt/server_args.py
index 14c337d6f..0e4b628b4 100644
--- a/python/sglang/srt/server_args.py
+++ b/python/sglang/srt/server_args.py
@@ -6844,9 +6844,12 @@ class ServerArgs:
             "--disaggregation-ib-device",
             type=str,
             default=ServerArgs.disaggregation_ib_device,
-            help="The InfiniBand devices for disaggregation transfer, accepts single device (e.g., --disaggregation-ib-device mlx5_0) "
-            "or multiple comma-separated devices (e.g., --disaggregation-ib-device mlx5_0,mlx5_1). "
-            "Default is None, which triggers automatic device detection when mooncake backend is enabled.",
+            help="The InfiniBand devices for disaggregation transfer. Supports a single device "
+            "(e.g., --disaggregation-ib-device mlx5_0), a shared comma-separated list "
+            "(e.g., --disaggregation-ib-device mlx5_0,mlx5_1), a per-GPU JSON mapping "
+            '(e.g., --disaggregation-ib-device \'{"0": "mlx5_0,mlx5_1", "1": "mlx5_2"}\'), '
+            "or a path to a JSON file containing that mapping. Default is None, which triggers "
+            "automatic device detection when mooncake backend is enabled.",
         )
         parser.add_argument(
             "--disaggregation-decode-enable-radix-cache",