第一步：备份你的原镜像文件，以免出错后可以恢复。
mv /etc/yum.repos.d/CentOS-Base.repo /etc/yum.repos.d/CentOS-Base.repo.bak
第二步：下载新的CentOS-Base.repo 到/etc/yum.repos.d/
wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.163.com/.help/CentOS6-Base-163.repo
如果无法下载可copy下面的PS内容
https://opsx.alibaba.com/mirror这个镜像是阿里云
wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-6.repo
第三步：修改gpgkey
gpgkey=http://mirrors.163.com/centos/RPM-GPG-KEY-CentOS-6，之前的用 “#” 注释
第四步：运行yum makecache生成缓存
yum clean all
yum makecache
本人亲测可以达到5M/s，实际情况根据个人网速。
PS:本人列出已经配置好的repo，大家可以直接复制内容到/etc/yum.repos.d/CentOS-Base.repo 即可使用。
# CentOS-Base.repo
#
# The mirror system uses the connecting IP address of the client and the
# update status of each mirror to pick mirrors that are updated to and
# geographically close to the client. You should use this for CentOS updates
# unless you are manually picking other mirrors.
#
# If the mirrorlist= does not work for you, as a fall back you can try the
# remarked out baseurl= line instead.
#
#
[base]
name=CentOS-$releasever - Base - 163.com
baseurl=http://mirrors.163.com/centos/$releasever/os/$basearch/
#mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=os
gpgcheck=1
#gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-6
gpgkey=http://mirrors.163.com/centos/RPM-GPG-KEY-CentOS-6
#released updates
[updates]
name=CentOS-$releasever - Updates - 163.com
baseurl=http://mirrors.163.com/centos/$releasever/updates/$basearch/
#mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=updates
gpgcheck=1
#gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-6
gpgkey=http://mirrors.163.com/centos/RPM-GPG-KEY-CentOS-6
#additional packages that may be useful
[extras]
name=CentOS-$releasever - Extras - 163.com
baseurl=http://mirrors.163.com/centos/$releasever/extras/$basearch/
#mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=extras
gpgcheck=1
#gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-6
gpgkey=http://mirrors.163.com/centos/RPM-GPG-KEY-CentOS-6
#additional packages that extend functionality of existing packages
[centosplus]
name=CentOS-$releasever - Plus - 163.com
baseurl=http://mirrors.163.com/centos/$releasever/centosplus/$basearch/
#mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=centosplus
gpgcheck=1
enabled=0
#gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-6
gpgkey=http://mirrors.163.com/centos/RPM-GPG-KEY-CentOS-6
#contrib - packages by Centos Users
[contrib]
name=CentOS-$releasever - Contrib - 163.com
baseurl=http://mirrors.163.com/centos/$releasever/contrib/$basearch/
#mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=contrib
gpgcheck=1
enabled=0
#gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-6
gpgkey=http://mirrors.163.com/centos/RPM-GPG-KEY-CentOS-6