Aiming at the nonlinear and time-delay issues in the pressure control system of the hydrocracking distillation process, a method is proposed to optimize the parameters of the PID controller by changing the calculation method of the learning factor in the particle swarm algorithm. The simulation results in MATLAB demonstrate that the improved PSO-PID algorithm outperforms the traditional PID control algorithm in terms of settling time, overshoot, and disturbance rejection capability for the pressure control system of the flash drum. It reduces the overshoot to 3.22% and shortens the settling time to 51.844 seconds, thereby optimizing the dynamic and static characteristics of the flash drum pressure in the system.