The invention discloses a numerical control system for a roll grinder and a control method thereof. The numerical control system comprises a communication interface card, a main shaft, an electric control device, a speed unit, a position detecting device, main-shaft motor machine tool electric appliance equipment and a feeding motor as well as a PC (Personal Computer) which is connected with the communication interface card; and the PC comprises a man-machine interface module and a real-time task module which are connected, wherein the man-machine interface module comprises a man-machine interface module body and a roll grinder grinding and machining module which is connected with the man-machine interface module body. The control method comprises the steps of selection, production, checking, explanation, interpolation and position control. By adopting the numerical control system, operators can once generate a numerical control program meeting system requirements for machining so that working efficiency is improved, and the reliability and the safety of the program are improved.