Ecological stoichiometric ratios of C, N and P are important characteristics of the process, and function of ecological system. robinia pseudoacacia featuring fast-growing, strong adaptability and tolerance of aridity and sterility, is a major tree species in reafforestation for soil and water conservation in the Loess Plateau.With robinia pseudoacacia forests on the Loess Plateau as subject, a study was carried out on ecological stoichiometry of carbon, nitrogen and phosphate in leaf-litter-soil systems different in aspect and their correlations. Results show that: On both shady and sunny slopes, in term of C:N, the three components of the systems were in order of leaf > litter > soil, while in term of C:P and N:P in the order of litter > leaf > soil. There was no significant difference between sunny and shady slope in C:P，C:N and N:P in leaf，litter and soil (p>0.05); but there were between the two in leaf，litter (p<0.05). In soil C:P，C:N and N:P were all higher in the 0～10cm soil layer than in the 10～20cm soil layer, but the difference was not significant(p>0.05); No matter on sunny or shady slope, leaf was positively related to litter in C:N. On sunny slope, the positive correlation between leaf and litter in N:P was significant. While, on shady slope, the positive correlation between litter and soil in C:N was in the 0～10cm soil layer.