Constant Market Share Model is used to analyze the reasons for service export growth at two different stages before and after China’s WTO entry since 1997, the results show that the expansion of the world market’s demand for services and the improvement of the competitiveness of China’s service are the foremost formative factor for for increased services export, however, the long-term change of the world service export structure impedes the export growth of China’s service to some degree, furthermore, the contribution of the interchange between China’s service export structure and the global service export structure to China’s service export growth is small but is obviously big after China’s WTO entry. China should break through service industry monopoly or introduce competitive mechanism to service industry to some extent while improve service export structure, raise service export industry operating efficiency so as to let China’s service export with more international competence.