Removing Mob Spawning at Spawn

Is there a way to remove mob from spawning in a particular area?
So I could remove the mob at the spawn.

You’ll need a region protection type plugin like FoxGuard or GriefPrevention. There may be more plugins that can do the job (eg UniverseGuard, RedProtect, …), see for yourself.

I do have GriefPrevention, how is it possible with it?

Hmmm. I thought that was what the entity-spawn flag was for, but (on reading the GP wiki) that might not be enough. You may need to ask on the GP thread. Otherwise, FoxGuard should be able to do the job.