Abstract: Wastewater Treatment Process (WWTP) is a multivariable and strong coupled nonlinear system. This paper proposes a fuzzy neural network controller based on Differential Evolution (DE) and Back Propagation (BP) algorithm, which is used to control the Dissolved Oxygen (DO) in WWTP. The fuzzy neural network is firstly off line optimized by DE and BP algorithm, and then is further on line adjusted by means of the local searching ability of BP algorithm. The proposed controller is used to control the DO of a benchmark WWTP BSM1 (Bechmark Simulation Model No.1). The experiment results show that the present algorithm can attain better performance than the conventional fuzzy controller.