Abstract: In order to improve the precision of temperature control for inertia instruments, and aiming at the influence of temperature control system on the stability generated by pure delay element, an optimization design method of temperature control system with a FirstOrder Delay Inertial Element is put forward. This method takes advantage of the balance of the bridge to eliminate temperature tracking error and uses the pulse width modulation (PWM) to increase heating efficiency. At the same time, based on ZieglerNichols setting, it uses the optimization design of PID controller to improve the phase margin of the temperature control system. These approaches enhance the adaptation ability of the temperature control system to the parameters of different instruments. The experimental results show that the temperature control precision is 0.006 ℃（1σ）under laboratory conditions and under the laboratory conditions of temperature cycle with forced convection. This method is simple, effective and easy to select the parameters of resistancecapacitance, at the same time it can meet the high precision requirement for temperature control.

Key words: delay inertia element, temperature control, PID setting, optimization design