mix signal pcb
subramanya.ap,
I believe you mean ground plane, which consists of grounded copper either between traces or a solid plane of copper between layers of a printed wiring board. The answer is yes, it will help. The ground plane provides a termination point for electric fields. The ground plane will help reduce both susceptibility to EMI and emissions from your circuit. The ground plane will not, however reduce EMI caused by currents that result in magnetic fields.
Regards,
Kral