diff --git a/src/opr-mm/impl/collective_comm.cpp b/src/opr-mm/impl/collective_comm.cpp
index 28a7412623fc78077dee1e610a00eb4c7a3abc88..f77f382792e8430700035ca3292be0a827273b38 100644
--- a/src/opr-mm/impl/collective_comm.cpp
+++ b/src/opr-mm/impl/collective_comm.cpp
@@ -410,6 +410,11 @@ CollectiveComm::CollectiveComm(
     ModeTrait::from_mode(param.mode).add_output_var(this, inp_cn);
     m_megray_ctx = MegRay::CudaContext::make(get_stream(output(0)));
 
+    const char* c_debug = MGB_GETENV("MGE_MM_OPR_DEBUG");
+    if (c_debug != nullptr and strcmp(c_debug, "1") == 0) {
+        m_debug_mode = true;
+    }
+
     add_equivalence_component<PODHash<Param>>(&m_param);
     add_equivalence_component<PODHash<size_t>>(&m_nr_devices);
     m_hash = XXHash{}.update(key.data(), key.size() * sizeof(char)).digest();
@@ -536,6 +541,11 @@ void CollectiveComm::do_execute(ExecEnv& env) {
         opr_register();
         cn.activate();
 
+        if (m_debug_mode) {
+            mgb_log_debug("collective comm: executing %s, rank = %d, key = %s",
+                    cname(), rank(), key().c_str());
+        }
+
         owner_graph()->event().signal_inplace<cg::event::BeforeKernel>(this, cn);
         trait.exec(this);
         owner_graph()->event().signal_inplace<cg::event::AfterKernel>(this, cn);
diff --git a/src/opr-mm/include/megbrain/opr/collective_comm.h b/src/opr-mm/include/megbrain/opr/collective_comm.h
index 0af65cfc1ddde111dd5baa79fd7ba994e3fc6b0e..9edc37d8f18a6d362d67a82dda5b4a1ce9d7b71a 100644
--- a/src/opr-mm/include/megbrain/opr/collective_comm.h
+++ b/src/opr-mm/include/megbrain/opr/collective_comm.h
@@ -123,6 +123,7 @@ private:
     std::shared_ptr<MegRay::Context> m_megray_ctx;
     std::shared_ptr<MegRay::Communicator> m_megray_comm;
     bool m_init = false;
+    bool m_debug_mode = false;
 
     //! dev buffers for each outputs
     SmallVector<std::shared_ptr<DeviceTensorND>> m_dev_buffers;