This paper investigates the robust control problem of the uncertain unified chaotic systems subject to sector input nonlinearity. First, the adaptive parameter is introduced for designing sliding surface such that the parameters of the unified chaotic system are not necessary to know. Then, based on Lyapunov theory, the controller is designed via sliding mode technique, which cancels the assumption that the information on the bound of input nonlinearity should be known for designer in advance. Finally, the sliding mode controller is applied to ensure that different uncertain chaotic systems (Lorenz system, Lü system and Chen system) states can be regulated to zero levels asymptotically in the presence of sector input nonlinearity. The simulation results demonstrated the effectiveness of the proposed controller.