Objective To study stress distribution of silastic membrane in dynamic mechanical cell strain unit by self-developed to know about stress of cells at different location. Method 3D Finite element method analysis with software ANSYS 8.0.was made. Based on axis symmetry theory, the model with DOF constraint and displacement load was established to simulate the practical condition for the silastic membrane under the tension. Results The Von mises stress nephogram, displacement nephogram and stress value were obtained via software ANSYS. Conclusion Stress in ring-shaped area is lower than that in marginal and central area with strain of 1%, 5% and 10%. Stress in central and ring-shaped area with 20% and 25% strain looks approximately close to each other but thestress value in central area is still more than that in ring-shaped area.