In this paper, the variable spray application system is examined as the research object. The control principle of the application system is explored, and its mathematical model is established. The second-order nonlinear ADRC and the model-compensated ADRC are designed for pressure and flow control, respectively. The superiority of these control algorithms is verified in the precision application system. This study also investigates the optimization of ADRC controller parameters for flow compensation using the PSO algorithm and for pressure loop. Simulation results indicate that both the dynamic and static performance, as well as the anti-interference performance of the PSO-ADRC control system, are significantly superior to those of PID control and ADRC control. Experimental results analysis demonstrates that the control of precision application system spray using the PSO-ADRC algorithm outperforms PID and ADRC under various pressure and flow rate conditions.