According to Gibrat?s law the growth of firms is independent of the size of firms.Based on the theory of industrial organization,competition strategy and externalities this paper discusses the applicability of Gibrat?s law to Chinese life industry,the relation between size and growth of life insurance companies and the main influence factors to size and growth.The findings imply: (1) Gibrat?s law is not consistent in Chinese life industry; (2)there is a convergence effect in the growth rate of premium and capital of life industry; (3)the Industry characteristic,business structure and externalities have a significantly effect to the size and growth of life companies.