The invention discloses a PI control loop performance evaluation method with the controller output constraint. In a control loop, the controller output difference constraint is introduced to limit the variation of a controlled object. Meanwhile, the fluctuation frequency and the fluctuation range of the controlled object are limited by restraining the output difference of a controller, so that the controlled object does not fluctuate violently. Meanwhile, the output difference of the loop is as small as possible, so that the interference of the external disturbance to the loop is reduced. According to the technical scheme of the invention, the optimization range of PI parameters is gradually expanded, and the region is gradually enlarged. A minimum output difference is found in the defined region. In this way, found PI parameters can be guaranteed to have good application prospect in the minimum output difference performance evaluation. Meanwhile, the optimization result is ensured not to enable the output variation of the controller to be too large. As a result, two optimization targets can be taken into consideration at the same time, and a powerful guarantee is provided for the efficient, green and low-energy-consumption production of enterprises.