According to the strong electromechanical coupling characteristic of numerical control machine tool driving system, sensorless information characteristic obtaining technology was discussed, and a kind of hardware modulating technology was put forward for incipient fault detection of driving system. Aiming at the non-linear and non stationary characteristics of sensorless information, EMD and EEMD methods were proposed to monitor the state and detect the faults of the driving system. This is the base of numerical control machine tool driving system performance evaluation by sensorless information.