i have bought an vps connect with root access and i need to use cpanel is there is any good open source controlpanel like cpanel.....
I would guess that there isn't anything quite as full-featured or as supported by 3rd-party add-ins as the commercial control panels like cPanel.
I looked into this myself a while ago (when setting up a small server for friends - in the end I just set things up manually and they are happy to put up with lack of flexibility, needing to ask me for changes and wait until I have time, as their needs are very simple) and DTC from GPLHost seemed to be the most promising of the F/OSS options by quite a margin - see here and here for info. I also bookmarked GNUPanel at the time, though that doesn't seem to be as complete or as actively maintained, and another that definitely seems to be a dead project now.
DTC is included in Debian's package repositories since Lenny and in Ubuntu's "universe" repository since Hardy, which might ease installation and future upgrades if your VPS is built using one of these distributions.
Be warned though: being a responsible server administrator is much more than just installing and configuring a control panel. You should make sure you are able to manage the server more manually if things go wrong and that you are aware of relevant security issues that will crop up from time to time.
I tried Plesk (it's cheaper, but still commercial, dont' know if it's open source) a long while ago. It was a terrible experience: slow, poor featured, useless. I went back to cPanel stright away. This is only my personal opinion.