Continuous stirred tank reactor (CSTR) is widespread highly nonlinear, instability and parameter uncertainty. Linear PID control algorithm is difficult to meet the control requirements of CSTR system. In order to improve the control quality of CSTR system, the proportion, integral and differential coefficients of linear PID controller are constructed by nonlinear function, and the nonlinear PID (NPID) control algorithm is obtained, and the NPID algorithm is applied to the temperature control of CSTR system. The simulation results show that the NPID control algorithm has better control effect, the CSTR discharge temperature and concentration response curves are smoother, the transition process time is shorter, and the system has stronger anti-interference ability and robustness.