Abstract: The C, N and P stoichiometric characteristics of tree litter soil of natural Populus davidiana secondary forest in Saihanwula area of Southern Daxinganling (semi-arid region) were analyzed, and the correlation between the growth decline of Populus davidiana forest and nutrient limitation was discussed, so as to provide theoretical basis for the restoration and reconstruction of natural forest resources. According to the different growth decline degree, Populus davidiana was divided into healthy growth, mild and severe decline growth. The contents of C, N and P in tree litter soil were measured, and the differences of stoichiometric characteristics of different components of Populus davidiana and the effects of growth decline on stoichiometric characteristics were analyzed. Result: (1) The contents of soil organic C and total N in the study area were higher than the average levels, and the content of soil total P was lower than the average level of forest soil in China. The contents of total N and total P in the rhizosphere soil of Populus davidiana with severe growth decline were significantly lower than those in the rhizosphere soil of normal growth Populus davidiana. (2) The C content of root was higher than that of the other organs of Populus davidiana; The ratios of C/N and C/P of Populus davidiana leaves with severe growth decline were higher than those of normal growth Populus davidiana, which indicated the N and P limitation in the growth process of Populus davidiana with severe growth decline. (3) The P reabsorption rate of normal growth Populus davidiana was significantly higher than that of Populus davidiana with severe growth decline. This indicated that P reabsorption by Populus davidiana leaves compensated for P deficiency in plant rhizosphere soil, which would be better for improving the plant drought resistance and the adaptability to drought environment. (4) The content of C, N and P in the litter leaves of Populus davidiana is at the average level of most terrestrial plants in the world and China.The C / N ratio of Populus davidiana litter was significantly higher than the critical point of nutrient N release, and the C / P ratio of Populus davidiana litter with severe growth decline was significantly higher than the critical point of nutrient P release, which indicated that N and P elements in the litter were not easy to decompose and release, which made n and P elements in the litter of Populus davidiana forest with severe growth decline largely retained, while some nutrient elements in the soil were consumed but not replenished in time. Therefore, the growth process of Populus davidiana was limited by nutrients, which was related to the organic forms of N and P elements in soil and the decomposition rate of litter leaves.