According to the character of induction motor under the high speed field weakening operation, a new method of good-performance flux observer is proposed based on the improved voltage model. Based on the current model in the rotor flux orientation, a flux observer compensator is designed. It solves the problem of the inaccurate flux observer because of the variable excitation field. According to the flux, the rotor speed is estimated using the simple and easy identification algorithm on Fixed-chip. Finally, the method combined with the flux observer and speed estimator is applied in the speed senseless vector control system. The simulation results show that the method is easy to implement, and can improve the accuracy of the observer speed and improve the performance of the control system.