Abstract: Free piston Stirling cryocooler(FPSC) has the advantages of efficient and compact, it is suitable for middle and low temperature refrigeration. In this paper, a 1-D model had been built to study FPSC used in low temperature freezer. The performance of FPSC are obtained by simulation and optimization. Under the conditions of different dead volumes, the influences of the PV power and phase angle on the machine performance are simulated in detail, and an optimal phase angle is got. In the paper, the effect of different regenerator materials and filling methods on the axial heat conduction losses of the regenerator and cooling performance of FPSC are also studied. The effects of the porosity of regenerator on the cooling capacity is obtained under different cooling temperatures. The influence of porosity on irreversible loss of regenerator are calculated and analyzed, and the optimal porosities are obtained under different cooling temperatures. At last, in order to obtain good cooling performance the parameters of regenerator and clearance seal are optimized in different cooling temperature.