1. install depended package on CendOS:

yum install gtk-vnc-python gtk-vnc pygtk2 rrdtool

2. download OpenXenManager from git

git clone https://github.com/OpenXenManager/openxenmanager.git

3. run

cd /usr/share/openxenmanager;
python openxenmanager

Refer to :

http://blog.centralserv.co.uk/install-openxenmanager-in-linux-mintubuntu/

http://cloudhero.blogspot.tw/2013/08/installing-openxenmanager-on-centoslinux.html

http://www.hostloc.com/thread-230403-1-1.html