Guanyin and Dashi Zhi are both one of the “ Western Trinity” . However, there are significant differences in both of faith’ s developments in China. Therefore, this study investigates the causes of the differences in faith’ s developments of Guanyin and Dashi Zhi in China. By the method of literature analysis and comparative study, investigator analyzes the subject in four aspects: faith’ s development, translated sutra, practice dharma, dissemination of folk custom. Through these analyses, further inductive causes of the differences are: qualities of Guanyin’ s faith are diverse, extroverted and comprehensive, and qualities of Dashi Zhi’ s faith are specialization, introverted and single. So, these resulted in the differences in faith’ s developments of Guanyin and Dashi Zhi in China.