步驟：
1.
gem sources --remove https://rubygems.org/
2.
gem sources -a https://ruby.taobao.org/ Error fetching https://ruby.taobao.org/: SSL_connect returned=1 errno=0 state=SSLv3 read server certificate B: ce rtificate verify failed (https://rubygems-china.oss-cn-hangzhou.aliyuncs.com/spe cs.4.8.gz)
3.
gem sources -l *** CURRENT SOURCES ***
問題來源：
http://stackoverflow.com/questions/4528101/ssl-connect-returned-1-errno-0-state-sslv3-read-server-certificate-b-certificat
https://gist.github.com/fnichol/867550
I had this same issue while working on a Ruby project. I am using Windows 7 64bit. I resolved this by: Downloading the cacert.pem file from http://curl.haxx.se/ca/cacert.pem. Saved that file to C:/RubyCertificates/cacert.pem Then set my environmental variable "SSL_CERT_FILE" to "C:/RubyCertificates/cacert.pem" source: https://gist.github.com/fnichol/867550
證書網址：http://curl.haxx.se/ca/cacert.pem
依照上面這位網友的方法配置了環境變數如下圖
再執行gem sources -a https://ruby.taobao.org/
報錯依舊
有誰遇過，還是我的環境變數沒有配置對呢？
現在淘寶的gem停止更新維護了，目前是ruby-china維護。
gem source --remove https://ruby.taobao.org/ --add http://gems-china.org/
gem source --add http://rubygems.org/gem source -l遇到相同問題，依照https://gist.github.com/fnichol/867550 的步驟執行後順利通過（需要註銷機子）。
不過我是加到系統變量，不知道是不是這個原因。
要加入系統變量，重啟電腦再執行切換淘寶源的指令就可以了