Abstract: In order to improve utilization ratio C₂H₄ in the reaction of C₂H₄ O, mass spectrograph with high precision and stability of temperature control is required to analyze utilization ratio of C₂H₄, The paper presents that the fuzzy-PID combined method is adopted to control temperature of reactor. Actual test and Matlab simulation are used at the same time. The results show that the control method can improve control accuracy and utilization ratio of C₂H₄, and shorten the system response time and system design time.