An adaptive active radial basis function (RBF) sliding mode controller is designed to control a unified chaotic system with parametric uncertainties under external disturbance. The controlled system is divided into a controllable subsystem and a free subsystem. Based on the controllable canonical form of controllable sub-systems state errors at the target points, a sliding surface is defined as the only input to the RBF controller. The weight of the controller is tuned on-line based on the sliding mode reaching law. The simulation results show that this method is applicable and effective, and the robustness to parametric uncertainties and external disturbance is provided. And the chattering of conventional sliding controls doesn’t occur.