Now I have a old CentOS distribution installation on one of my VPS. It is CentOS 5.11.
I use Crontab for schedule jobs. When I install this VPS and try to config crontab, I can not find it in Webmin. crontab is installed.
After google it and finally found the answer.
I have to install vixie-cron package. So run following command as root.
1) Install vixie-cron
yum install vixie-cron
2)Start Crond service
service crond start
3) Make it auto start on boot
chkconfig crond on