The invention provides an MPC secondary frequency modulation active allocation method based on time-variable load disturbance. The method comprises the steps of (1) giving a continuous-time state-space model of a system based on a dynamics equation in the controlled system; (2) converting the continuous-time state-space model into a discrete model and determining a sampling period T; (3) establishing an MPC model considering the time-variable load disturbance in a future domain of time; and (4) solving the MPC model. The invention fully considers the presence of constraints in the system and future load time-variable characteristics, gives an anti-interference control input satisfying the system constraint at every moment, has high safety and reliability, and can better resist external load fluctuations and show higher robustness as compared with conventional PI control.