Abstract: In order to improve the control performance of the dissolved oxygen (DO) concentration and nitrate nitrogen (S_NO) concentration in a wastewater treatment plant (WWTP), an optimal control strategy based on iterative adaptive dynamic programming (ADP) algorithm was proposed. It only need the input and output of the non-linear dynamics model of the control system, and approximate the performance evaluation index and optimal control strategy by networks identifying the control system. The learning algorithm of controler was implemented on line in the benchmark simulation model(BSM1). Finally, the experiments validate the effectiveness of the proposed control strategy in improving the control precision and system robustness compared to the traditional PID control strategy.