This paper analyses the synchronization control for a class of master_slave chaotic systems with parameter uncertainties,external noise disturbances and sector nonlinear input.It designs a class of sliding mode controllers for chaos synchro nization,testifying theoretically that the effectiveness of the controller is be yond the impact from the parameter uncertainties and external noise disturbances of the system under control and thus it is of strong robust nature.Finally,the effectiveness of this kind of controller is also proved by numerical simulations for the master_slave Duffing_Holmes systems.