Based on the effects of temperature upon the material properties of cylindrical shells,this paper established a geometrical nonlinear dynamic control equation of cylindrical shells under disturbing external pressure,and studied the bifurcation of cylindrical shells under thermal load and disturbing external pressure by using Galerkin's principle and Melnikov's method. It also discussed the effects of temperature, Batdorf's parameter etc. upon the chaotic motion region of cylindrical shells. The results show that the chaotic motion region enlarges when the temperature or the Batdorf's parameter increases.