With Mosuo's sacred natural sites of mountainous forest in Yongning-Lugu Lake area as the research subject,by using the method of ecology,the vegetation type in this area was initially identified.The control sample plot of the same vegetation type at similar altitude and in similar soil condition would be selected and compared with the sample plot in sacred natural sites at length,so as to quantitatively analyze the protection of biological diversity in the perspective of ecological system.It showed that under the circumstance of the damage of ecological environment,complete natural vertical pattern was preserved thanks to sacred natural sites of mountainous forest established by reason of traditional religion and culture.The results of research and quantitative analysis showed that compared with the control sample plot of the same vegetation type,sacred natural sites were high in biological diversity and the species composition of plant community in sacred natural sites was closer to that of primitive forest.The result of quantitative analysis also indicated that sacred natural sites played a remarkable role in protecting vegetation and this protective function became more remarkable if the altitude was higher.And human were reminded to pay close attention to the preservation and protection function of sacred natural sites to natural ecological system at high altitude.