Aiming at the system with pure time lag, the shortcomings of PID algorithm, Smith estimation method and fuzzy control are analyzed, and a new fuzzy composite controller is proposed, which is based on the fuzzy-PID controller estimated by Smith, which uses Smith preestimation method to overcome pure hysteresis, uses fuzzy control to improve the robustness of the system, and switches to PID control in the steady-state stage to improve the control accuracy. The simulation study is carried out in the case of model matching and mismatch, and the results show that the composite controller not only has the strong robustness of fuzzy control but also has the characteristics of high PID control accuracy, especially when the model mismatches, it shows good stability and robustness, and is a practical and simple control method for large time lag systems.