To improve the disturbance rejection property of permanent magnet syn-chronous motor (PMSM) speed control system, the integral sliding mode control (ISMC) method is introduced in the control design of speed loop. However, the simulation and implementation results show that it is difficult to balance the chattering and the anti-disturbance capacity. To this end, three kinds of improved ISMC control methods are developed. First, ISMC using linear varying gain is developed. Using this method, the switching gain of ISMC controller can be smaller while still ensuring that the speed state reaches its steady state and the steady state fluctuations can thus be reduced. Moreover, the anti-disturbance capacity of the PMSM system can also be assured. Second, an in-tegral sliding mode control based on extended state observer (ESO) is developed. ESO can estimate both of the states and the disturbances simultaneously. By using ESO, an estimate of the lumped disturbances is obtained, which is employed for the feedforward compensation design of the composite ISMC control law. In this case, the controller may take a smaller value for the switching gain without sacrificing disturbance rejection per-formance, which helps to reduce large chattering caused by high control gains. Third, an adaptive composite control method combining linear varying gain and ESO is developed to take advantages of both improved methods. These improved methods show advantages in reducing the chattering while ensuring the dynamic and disturbance rejection perfor-mance. Both of simulation and experiment results are provided.