Abstract: Naiman Desertification Research Station, site conditions of Populus simoni–Pinus sylvestris var. mongolica mixed forests as experimental sample, using spatial structure parameters of unary distribution and ternary distribution of P. simonii–P. sylvestris var. mongolica mixed forest spatial structure characteristics, using Ripley's K function analysis of P. simonii–P. sylvestris var. mongolica mixed forest spatial distribution pattern and interspecific association. The results show that the number of plants of P. sylvestris var. mongolica was mainly concentrated in 12 cm diameter class, and that of . simonii was mainly concentrated in 6 cm diameter class. The Angle index of P. simoni–P. sylvestris var. mongolica mixed forest is 2/3 random distribution and 1/3 aggregate distribution. The neighborhood comparison of the size ratio is uniform, and it is mainly a mean distribution. Mingling was small, mainly between weak degree of mixed and moderate mixed. When M and U keep unchanged, with the increase of W, P. simonii–P. sylvestris var. mongolica mixed forest with W=0.5 the relative frequency for axial present normal distribution; when W and M remain constant, U distribution of P. simonii–P. sylvestris var. mongolica mixed forest forest is in the range 0, 0.25 > 0.75, 1. At the spatial scale of 0–25 m, P. simonii and P. sylvestris var. mongolica populations were mainly distributed randomly and aggregated, and the random distribution accounted for most of them. P. simonii and P. sylvestris var. mongolica populations were mainly uncorrelated. P. simonii–P. sylvestris var. mongolica mixed forests is a kind of artificial and natural mixed forest, the horizontal distribution pattern is random distribution, the neighborhood comparison is medium distribution, mingling is medium mixed, and the interspecific correlation competition between P. microphylla and P. sylvestris var. mongolica is weak. Therefore, reasonable adjustment and optimization of stand spatial structure can make succession develop in the ideal direction.