1.首先彻底关闭Mac App Store软件
2.在终端输入以下代码(需要输入密码,密码隐藏看不见):
sudo defaults write /Library/Preferences/com.apple.SoftwareUpdate CatalogURL https://swscan.apple.com/content/catalogs/others/index-10.10seed-10.10-10.9-mountainlion-lion-snowleopard-leopard.merged-1.sucatalog.gz
3之后再次直接或者重启后打开Mac App Store检查更新尝试