You want a captcha protected wplogin or wpadmin login? then use this plugin
安装:
Download the wp-login captcha then paste it the plugin directory or download it via plugin area of admin's backend search for "wplogin-captcha". Then go to settings set google API key, you can get the API key here www.google.com/recaptcha
常见问题:
Is recaptcha v2 and invinsible captcha has same API key?
NO, they dffrnt you need to get API key for each of them
I'm working in localhost then migrate my website to live, how to fix captcha error?
before migrate deactivate the plugin, then get new API key for the new URL