Establishment of nature reserves is one of the best ways to protect speciesbiodiversity. The effect of protecting species was analyzed in this study by selecting 40 important and typical nature reserves in Southwest Chinawith the aim of providing evidence for the management on nature reserves. Main results were as follows: (1)The number of wild animals and plants species protected in reserves increased logarithmically with the increase of nature reserves. By this way the total number of wild vertebrates protected in nature reserves of the Southwest were estimated as 2426, occupying 38.2 percent of total wild vertebrates species in China. (2) Wild higher plants species protected in nature reserves of the Southwest were 20965, which were almost 70 percent of total wild higher plants species in China. (3) It showed that the number of plant and animal species protected in reserves was positively linearly related to the area of reserves when below 1.5 million ha, and almost kept unchanged above that area. This indicates that the habitats of other endemic wild species beyond the species in the existing reserves should be considered in the establishment of new nature reserves. (4) The total number of China′s important species protected in the reserves of Southwest China was also established: wild animals protected were 119, of which 42 were in Class I and 77 were in Class II, taking 46.3% of total national important animal species in China. The wild plants protected were 138, of which 29 in Class I and 109 in Class II, occupying 54.3% of total national important plant species.