#75 楼 @QueXuQ 我的 yard-0.8.3 也是出现了同样的问题，卸载了当前的 yard 然后重新安装了当前最新版 yard-0.8.76 就 OK 了。

--- rails_projects/genghis » gem -v
Error loading RubyGems plugin "/Users/HuangKai/.rvm/gems/ruby-2.1.5/gems/yard-0.8.3/lib/rubygems_plugin.rb": cannot load such file -- rubygems/doc_manager (LoadError)
2.4.5
--- rails_projects/genghis » gem uninstall yard -v 0.8.3
Error loading RubyGems plugin "/Users/HuangKai/.rvm/gems/ruby-2.1.5/gems/yard-0.8.3/lib/rubygems_plugin.rb": cannot load such file -- rubygems/doc_manager (LoadError)
Remove executables:
    yard, yardoc, yri

in addition to the gem? [Yn]  y
Removing yard
Removing yardoc
Removing yri
Successfully uninstalled yard-0.8.3
--- rails_projects/genghis » gem install yard
Fetching: yard-0.8.7.6.gem (100%)
Successfully installed yard-0.8.7.6
1 gem installed
--- rails_projects/genghis » gem -v
2.4.5