Ecological stoichiometry focuses on the balance of chemical elements in ecological processes, in which the stoichiometric characteristics of carbon (C), nitrogen (N) and phosphorus (P) in different components are important features of ecosystem functions and processes. At present, it is not clear how the introduction of Hippophae rhamnoides (N-fixing) affects the nutrient cycling mechanism of ecosystem in N-fixing or non-N-fixing pure plantations. Therefore, two kinds of mixed forests (H. rhamnoides + Pinus tabuliformis, H_rP_t; H. rhamnoides + Robinia pseudoacacia, H_rR_p) and the pure forests of P. tabuliformis (P_t) and R.pseudoacacia (R_p) were selected. The C, N and P contents in leaf, litter and 0—100 cm soil layer were quantified, and the effects of mixed afforestation on the synergistic variation of nutrients among different components were explored. The results indicated that:(1) Compared with P_t, the C, N, P contents (p<0.05) and the N∶P (p>0.05) increased, while C∶N and C∶P decreased (p>0.05) in the leaves of P. tabuliformis in H_rP_t, indicating that H_rP_t was helpful to relieve the restriction of N and accelerate its growth rate. Meanwhile, compared with R_p, the C, N, C∶P and N∶P decreased, while P and C∶N increased of R. pseudoacacia in H_rR_p (p>0.05), suggesting that H_rR_p might enhance the absorption of P by R. pseudoacacia, but the sequestration of C and N would be decreased. (2) The C, N, P contents and N∶P of the litters in H_rP_t were significantly higher than those of P_t, and the C∶N and C∶P values were significantly lower than those of P_t, indicating that H_rP_t was helpful to accelerate the decomposition rate of litter and promote nutrient return. Compared with R_p, the C, N, P contents and their stoichiometric ratios of the litters in H_rR_p increased (p>0.05), suggesting that H_rR_p did not significantly promote the decomposition of litter. (3) Compared with P_t and R_p, the soil C, N and P contents in H_rP_t and H_rR_p increased, but C∶N and C∶P decreased (p>0.05), indicating that H_rP_t and H_rR_p were helpful to increase the utilization efficiency of N and P and improve the soil nutrient status. (4) The main stoichiometric indicators between leaf and litter had a strong synergistic effect. In addition, the correlation of N and P elements in leaf, litter and soil was more obvious than that of the C element. In summary, compared with H_rR_p, H_rP_t was more helpful to improve the supply of nutrient limiting factors and accelerate the conversion of nutrients among different components. The research results are of great significance for revealing the nutrients supply potential of the artificial mixed forest ecosystem in the Loess Plateau and formulating a reasonable forest management plan.