Synthetic error of CNC machine tool, mainly including geometric error and thermal error, is generally affected by many factors. And temperatures that include environment temperature and temperature asymmetry of machine tool are most important factor. Aiming at geometric error and thermal error mainly, this paper proposed a real-time synthetic error compensation solution for CNC machine tool based on Differential Resolver Function (DRF). The principle of this solution is offsetting the origin of workpiece coordinate system when implementing the NC code in machine tool. After real-timely collecting machine tool coordinates position and thermal key points’ temperatures, synthetic errors are calculated by the synthetic model that is beforehand constructed and stored in compensation equipment, and then the pulses that represent coordinate system origin offsetting value are generated and sent into NC system by DRF to realize synthetic error compensation of CNC machine tool.