diff --git a/macro_string/README.md b/macro_string/README.md
index 3c31e87..ac6cdef 100644
--- a/macro_string/README.md
+++ b/macro_string/README.md
@@ -1,2 +1,5 @@
 use CMake to set string macro in file
 include diffrent file by cmake
+
+cmake>3.12
+can use:add_compile_definitions(TEST_A="test")