diff --git a/.readthedocs.yml b/.readthedocs.yml
new file mode 100644
index 0000000000..a105ddb2b2
--- /dev/null
+++ b/.readthedocs.yml
@@ -0,0 +1,3 @@
+version: 2
+conda:
+  environment: doc/environment.yml
\ No newline at end of file
diff --git a/doc/environment.yml b/doc/environment.yml
new file mode 100644
index 0000000000..f3928e4015
--- /dev/null
+++ b/doc/environment.yml
@@ -0,0 +1,10 @@
+name: RTD
+channels:
+  - conda-forge
+  - defaults
+dependencies:
+  - doxygen>=1.9.1
+  - python=3.9
+  - pip>=20.1
+  - pip:
+    - ..[docs,cpu]
diff --git a/setup.py b/setup.py
index 363cd0015f..d46703e463 100644
--- a/setup.py
+++ b/setup.py
@@ -127,7 +127,7 @@
     cmake_minimum_required_version="3.0",
     extras_require={
         "test": ["dpdata>=0.1.9", "ase", "pytest", "pytest-cov", "pytest-sugar"],
-        "docs": ["sphinx>=3.1.1,<4.1.0", "recommonmark", "sphinx_rtd_theme>=1.0.0rc1", "sphinx_markdown_tables", "myst-parser", "breathe", "exhale", "numpydoc", "ase"],
+        "docs": ["sphinx>=3.1.1", "recommonmark", "sphinx_rtd_theme>=1.0.0rc1", "sphinx_markdown_tables", "myst-parser", "breathe", "exhale", "numpydoc", "ase"],
         **extras_require,
     },
     entry_points={"console_scripts": ["dp = deepmd.entrypoints.main:main"]},