In order to realize the high dynamic performance of induction motor, a passive speed control scheme of induction motor based on fullorder state observer and speed adaptive estimation was proposed for the nonlinear nature of the motor. With the analysis of the passive of induction motor and the relationship between passive and stability, a scheme of asymptotic stability torque tracking controller was designed. In order to solve the problem that the rotor current was difficult to be observed, it was proposed that fullorder state observer was designed based on rotating coordinate and the rotor current and rotor flux were as the state variables. The observer was used to estimate the speed, so that the induction motor without speed sensor passive control could be achieved. The simulation results showed that the method was simple and effective, and the rotor current and speed were accurately estimated by the fullorder observer and effectively improve the dynamic and static performance of the induction motor.