A mechanical cryocooler is one of the important parts of an infrared detector. It provides a precise and stable low temperature operation environment for the infrared detector. In the engineering applications, the tuning of Proportion Integration Differentiation (PID) parameters is mostly dependent on the experience of engineers. Thus, the theoretical analysis of PID parameter design is lacked. The frequency-domain design method of PID control parameters is analyzed according to the Bode diagram, the Nyquist stable criterion and the control model of the cryocooler. The simulation results show that this method is reliable and effective and can provide guidance for the online tuning of PID temperature control parameters of mechanical cryocoolers.