Abstract: Studies were made of the stand spatial structure of mixed Pinus armandii Forest of different tree species in central Yunnan Plateau by means of three parameters,including the mingling intensity,uniform angle index and neighborhood comparison. The results showed that forest space isolation level was from low to high along with the fall of the tree species composition factor. The mixed degree of the stand was weak and zero when the composition factor was more than 6; The mixed degree of the stand was between middle and intensive when the composition factor was less than 6; The dominant tree species, Pinus armandii,was close to moderate mixture, and the rest species were intensive mixture. All of the stand belonged to the aggregate distribution; Average neighborhood comparison was between 0.47 to 0.51, belonging to the medium level. In general,the stand would grow more stable and better if the dominant tree species composition factor was low and the composition factor of each species was uniform.