Abstract: Basing on conbination of themlodynamic and dynamic of FPST,it is concluded that the stability of FPST is correlated with flow-damping factor of regenerator,damping factor between the piston and the displacer reciprocating pairs and the rigidity of the spring, a model of the computer aided phase angle trimming procechure basing on the vibration system analyses of FPST has been established. Being compared with the result,both the simulation and the experimentation results coincided satisfactorily.