diff --git a/source/module_elecstate/module_dm/density_matrix.cpp b/source/module_elecstate/module_dm/density_matrix.cpp
index bdd1947d627..53de6eb3e64 100644
--- a/source/module_elecstate/module_dm/density_matrix.cpp
+++ b/source/module_elecstate/module_dm/density_matrix.cpp
@@ -272,27 +272,6 @@ TK* DensityMatrix<TK, TR>::get_DMK_pointer(const int ik) const
     return const_cast<TK*>(this->_DMK[ik].data());
 }
 
-// get _DMK[ik] vector
-template <typename TK, typename TR>
-std::vector<std::vector<TK>> DensityMatrix<TK, TR>::get_DMK_vector() const
-{
-    return this->_DMK;
-}
-
-// get _paraV pointer
-template <typename TK, typename TR>
-const Parallel_Orbitals* DensityMatrix<TK, TR>::get_paraV_pointer() const
-{
-    return this->_paraV;
-}
-
-// get _kv pointer
-template <typename TK, typename TR>
-const K_Vectors* DensityMatrix<TK, TR>::get_kv_pointer() const
-{
-    return this->_kv;
-}
-
 // set DMK using a pointer
 template <typename TK, typename TR>
 void DensityMatrix<TK, TR>::set_DMK_pointer(const int ik, TK* DMK_in)
diff --git a/source/module_elecstate/module_dm/density_matrix.h b/source/module_elecstate/module_dm/density_matrix.h
index 1c758ae1395..62554018506 100644
--- a/source/module_elecstate/module_dm/density_matrix.h
+++ b/source/module_elecstate/module_dm/density_matrix.h
@@ -139,9 +139,11 @@ class DensityMatrix
      * @brief get pointer vector of DMR
      * @return HContainer<TR>* vector of DMR
      */
-    std::vector<hamilt::HContainer<TR>*> get_DMR_vector() const {return this->_DMR;}
+    const std::vector<hamilt::HContainer<TR>*>& get_DMR_vector() const {return this->_DMR;}
+    std::vector<hamilt::HContainer<TR>*>& get_DMR_vector() {return this->_DMR;}
 
-    std::vector<std::vector<TR>> get_DMR_save() const {return _DMR_save;}
+    const std::vector<std::vector<TR>>& get_DMR_save() const {return this->_DMR_save;}
+    std::vector<std::vector<TR>>& get_DMR_save() {return this->_DMR_save;}
 
     /**
      * @brief get pointer of DMK
@@ -153,7 +155,8 @@ class DensityMatrix
     /**
      * @brief get pointer vector of DMK
     */
-    std::vector<std::vector<TK>> get_DMK_vector() const;
+    const std::vector<std::vector<TK>>& get_DMK_vector() const {return this->_DMK;}
+    std::vector<std::vector<TK>>& get_DMK_vector() {return this->_DMK;}
 
     /**
      * @brief set _DMK using a input TK* pointer
@@ -164,9 +167,9 @@ class DensityMatrix
     /**
      * @brief get pointer of paraV
      */
-    const Parallel_Orbitals* get_paraV_pointer() const;
+    const Parallel_Orbitals* get_paraV_pointer() const {return this->_paraV;}
 
-    const K_Vectors* get_kv_pointer() const;
+    const K_Vectors* get_kv_pointer() const {return this->_kv;}
 
     /**
      * @brief calculate density matrix DMR from dm(k) using blas::axpy