Abstract: The results of investigation on the structure of the protective forest belt in sandy area in Maowusu indicate that the structures of the diameter at breast height(DBH)and the height of pure forest of Pinus sylvestris var. are more regular than those of the mixed forest. And it coincides with the changing rule of general species. The crown of the Pinus sylvestris var. is lower than that of mixed forest and P. tabulaeformis. And it decreases with the height of the tree increasing, forming a thick tree crown. According to the analysis, the forest square or the forest belt of the Pinus sylvestris var. should be developed in order to improve the ecological efficiency.