For example I have 3 desktop? like office,network and media.
need to run office applications on office desk, internet applications on desktop network and etc.
How to do it?
If you're comfortable having them start up when you start Xfce, just leave them open, bring up the logout screen, tick the little 'save session' checkbox and log out, remembering to untick that checkbox the next time you log out. Each time you start Xfce up, it should remember the apps and their workspaces.
Alternatively, you can use Devil's pie, or use custom scripts that launch the app and, at the same time, use a tool like wmctrl, or xdotool, to send the app to a specific workspace.