Abstract: The traditional finite control set model predictive control (FCS-MPC) outputs a single switching state in one control cycle. When the sampling frequency is low, the control accuracy is poor, and the switching frequency is not fixed, which makes it difficult to design the AC side filter. To solve the above problems, this paper proposes a constant frequency model predictive control based on power tracking objective function for the three-phase PWM rectifier on the basis of traditional FCS-MPC. Firstly, based on the minimum solution of the FCS-MPC power tracking objective function, the sector of the converter output voltage vector is accurately calculated, which determines the two effective vectors and the zero vector of the control period. And then the power tracking difference of the three vectors is utilized to calculate the action time of each voltage vector. Through simulation and compared with the traditional FCS-MPC, the proposed method can achieve fixed switching frequency, reduce power ripple and improve the output performance of the rectifier.