diff --git a/Specification.md b/Specification.md
new file mode 100644
index 0000000..0bc6b4e
--- /dev/null
+++ b/Specification.md
@@ -0,0 +1,4 @@
+### Configuration
+
+- All options should be put in `conf/app.ini` file in INI format.
+- All keys' name should use all upper cases and underscore except sections' name(e.g. `HTTP_PORT = 3000`).
\ No newline at end of file