1.备份源文件
cp /etc/apt/sources.list /etc/apt/sources.list.bak
2. 修改apt-get源文件
vi /etc/apt/sources.list
删除文件中所有内容，然后替换为如下内容；
deb http://mirrors.ustc.edu.cn/ubuntu/ xenial main restricted universe multiverse deb http://mirrors.ustc.edu.cn/ubuntu/ xenial-security main restricted universe multiverse deb http://mirrors.ustc.edu.cn/ubuntu/ xenial-updates main restricted universe multiverse deb http://mirrors.ustc.edu.cn/ubuntu/ xenial-proposed main restricted universe multiverse deb http://mirrors.ustc.edu.cn/ubuntu/ xenial-backports main restricted universe multiverse deb-src http://mirrors.ustc.edu.cn/ubuntu/ xenial main restricted universe multiverse deb-src http://mirrors.ustc.edu.cn/ubuntu/ xenial-security main restricted universe multiverse deb-src http://mirrors.ustc.edu.cn/ubuntu/ xenial-updates main restricted universe multiverse deb-src http://mirrors.ustc.edu.cn/ubuntu/ xenial-proposed main restricted universe multiverse deb-src http://mirrors.ustc.edu.cn/ubuntu/ xenial-backports main restricted universe multiverse
保存退出；apt-get update就可以了
