The finite element analysis model of packer rubber was established,the deformation process of three different types of rubbers,i.e.cylindrical rubber,trapezoidal rubber and semicircular rubber,was simulated,and the stability of different types of rubbers during constrained deformation was analyzed.A method was presented to judge the stability of rubbers by the simulation data,and the stable deformation of three different types of rubbers in the constrained stage was compared.The results show that with the increase of the ratio of height to diameter,the unstable deformation of three different types of rubbers will occur.The rubbers with support ring (trapezoid ring groove and half ring groove rubbers) is more prone to unstable deformation than the cylindrical rubber,and the stable deformation load needed by the semicircular ring rubber is larger than that of the trapezoid rubber.The material difference has little influence on the change trend of the stable deformation load,and only has influence on the value of the stable deformation load.