来源：http://blog.ubuntusoft.com/ubuntu-update-source.html#.Uq_PP9KBmxh
其它版本的修改方式相识。尽量使用原生工具来修改（见下方）。
手动修改方式：
163源
1 deb http://mirrors.163.com/ubuntu/ precise main restricted 2 deb-src http://mirrors.163.com/ubuntu/ precise main restricted 3 deb http://mirrors.163.com/ubuntu/ precise-updates main restricted 4 deb-src http://mirrors.163.com/ubuntu/ precise-updates main restricted 5 deb http://mirrors.163.com/ubuntu/ precise universe 6 deb-src http://mirrors.163.com/ubuntu/ precise universe 7 deb http://mirrors.163.com/ubuntu/ precise-updates universe 8 deb-src http://mirrors.163.com/ubuntu/ precise-updates universe 9 deb http://mirrors.163.com/ubuntu/ precise multiverse 10 deb-src http://mirrors.163.com/ubuntu/ precise multiverse 11 deb http://mirrors.163.com/ubuntu/ precise-updates multiverse 12 deb-src http://mirrors.163.com/ubuntu/ precise-updates multiverse 13 deb http://mirrors.163.com/ubuntu/ precise-backports main restricted universe multiverse 14 deb-src http://mirrors.163.com/ubuntu/ precise-backports main restricted universe multiverse 15 deb http://mirrors.163.com/ubuntu/ precise-security main restricted 16 deb-src http://mirrors.163.com/ubuntu/ precise-security main restricted 17 deb http://mirrors.163.com/ubuntu/ precise-security universe 18 deb-src http://mirrors.163.com/ubuntu/ precise-security universe 19 deb http://mirrors.163.com/ubuntu/ precise-security multiverse 20 deb-src http://mirrors.163.com/ubuntu/ precise-security multiverse 21 deb http://extras.ubuntu.com/ubuntu precise main 22 deb-src http://extras.ubuntu.com/ubuntu precise main
sohu源
1 deb http://mirrors.sohu.com/ubuntu/ precise main restricted 2 deb-src http://mirrors.sohu.com/ubuntu/ precise main restricted 3 deb http://mirrors.sohu.com/ubuntu/ precise-updates main restricted 4 deb-src http://mirrors.sohu.com/ubuntu/ precise-updates main restricted 5 deb http://mirrors.sohu.com/ubuntu/ precise universe 6 deb-src http://mirrors.sohu.com/ubuntu/ precise universe 7 deb http://mirrors.sohu.com/ubuntu/ precise-updates universe 8 deb-src http://mirrors.sohu.com/ubuntu/ precise-updates universe 9 deb http://mirrors.sohu.com/ubuntu/ precise multiverse 10 deb-src http://mirrors.sohu.com/ubuntu/ precise multiverse 11 deb http://mirrors.sohu.com/ubuntu/ precise-updates multiverse 12 deb-src http://mirrors.sohu.com/ubuntu/ precise-updates multiverse 13 deb http://mirrors.sohu.com/ubuntu/ precise-backports main restricted universe multiverse 14 deb-src http://mirrors.sohu.com/ubuntu/ precise-backports main restricted universe multiverse 15 deb http://mirrors.sohu.com/ubuntu/ precise-security main restricted 16 deb-src http://mirrors.sohu.com/ubuntu/ precise-security main restricted 17 deb http://mirrors.sohu.com/ubuntu/ precise-security universe 18 deb-src http://mirrors.sohu.com/ubuntu/ precise-security universe 19 deb http://mirrors.sohu.com/ubuntu/ precise-security multiverse 20 deb-src http://mirrors.sohu.com/ubuntu/ precise-security multiverse 21 deb http://extras.ubuntu.com/ubuntu precise main 22 deb-src http://extras.ubuntu.com/ubuntu precise main
使用方式：
sudo gedit /etc/apt/sources.list
然后把里面的列表替换成上面的列表，保存退出即可，修改完之后最好刷新一下系统的源：
sudo apt-get update
系统修改方式：
事实上，Ubuntu 已经收录了国内大部分知名的源，所以无需上网查找。
打开软件中心 – 编辑 – 软件源 ，然后点击源的列表 – 其他站点：
然后可以自己选择一个源，建议163源，比较稳定
选中后，点击右下角的选择服务器即可！