diff --git a/docs/advanced/input_files/input-main.md b/docs/advanced/input_files/input-main.md
index 40edbf5538..d8491bbf71 100644
--- a/docs/advanced/input_files/input-main.md
+++ b/docs/advanced/input_files/input-main.md
@@ -1389,7 +1389,7 @@ These variables are used to control the geometry relaxation.
 
 - **Type**: Integer
 - **Description**: The maximal number of ionic iteration steps, the minimum value is 1.
-- **Default**: 1
+- **Default**: 1 for SCF, 50 for relax and cell-relax calcualtions
 
 ### relax_cg_thr
 
diff --git a/source/module_io/read_input_item_relax.cpp b/source/module_io/read_input_item_relax.cpp
index f222b25ef9..e39abb57d0 100644
--- a/source/module_io/read_input_item_relax.cpp
+++ b/source/module_io/read_input_item_relax.cpp
@@ -58,7 +58,7 @@ void ReadInput::item_relax()
             }
             else if (calculation == "relax" || calculation == "cell-relax")
             {
-                if (!para.input.relax_nmax)
+                if (para.input.relax_nmax == 0) // default value
                 {
                     para.input.relax_nmax = 50;
                 }
diff --git a/source/module_parameter/input_parameter.h b/source/module_parameter/input_parameter.h
index bfd9ae91cb..db71d32b63 100644
--- a/source/module_parameter/input_parameter.h
+++ b/source/module_parameter/input_parameter.h
@@ -152,7 +152,7 @@ struct Input_para
     bool relax_new = true;
     bool relax = false; ///< allow relaxation along the specific direction
     double relax_scale_force = 0.5;
-    int relax_nmax = 1;        ///< number of max ionic iter
+    int relax_nmax = 0;        ///< number of max ionic iter
     double relax_cg_thr = 0.5; ///< threshold when cg to bfgs, pengfei add 2011-08-15
     double force_thr = -1;     ///< threshold of force in unit (Ry/Bohr)
     double force_thr_ev = -1;  ///< threshold of force in unit (eV/Angstrom)