Error using install under windows

hi@sbc100
When I use .\emsdk install 1.39.20 under windows, the following error occurs. I am using python3.7.5. What is the reason?

Traceback (most recent call last):
File "D:\Gitcode\emsdk/emsdk.py", line 3077, in
sys.exit(main())
File "D:\Gitcode\emsdk/emsdk.py", line 3057, in main
success = tool.install()
File "D:\Gitcode\emsdk/emsdk.py", line 1813, in install
return self.install_sdk()
File "D:\Gitcode\emsdk/emsdk.py", line 1830, in install_sdk
success = emscripten_npm_install(self, os.path.join(emsdk_path(), install_path, 'emscripten'))
File "D:\Gitcode\emsdk/emsdk.py", line 1246, in emscripten_npm_install
universal_newlines=True)
File "C:\ProgramFiles\Python37\lib\subprocess.py", line 411, in check_output
**kwargs).stdout
File "C:\ProgramFiles\Python37\lib\subprocess.py", line 488, in run
with Popen(*popenargs, **kwargs) as process:
File "C:\ProgramFiles\Python37\lib\subprocess.py", line 800, in __init__
restore_signals, start_new_session)
File "C:\ProgramFiles\Python37\lib\subprocess.py", line 1208, in _execute_child
startupinfo)
FileNotFoundError: [WinError 2] The system can not find the file specified.

so, what's the reason I can't find. Could you give me some suggestions?