To comprehensively understand the stoichiometric characteristics of different plantation ecosystems, field investigations and laboratory analyses were performed to study the carbon (C), nitrogen (N), and phosphorus (P) stoichiometries in the arbor, shrub, herb, litter, and soil (soil depth 0-100cm) of the deciduous broad-leaved tree species Robinia pseudoacacia and evergreen coniferous tree species Pinus tabuliformis plantations in the Loess hilly-gully region, northern Shaanxi, China. The results showed that 1) the C concentrations of arbor organs were significantly lower in Robinia than in the Pinus plantations, while the N and P concentrations were significantly higher in Robinia than in the Pinus plantations. Thus, the C:N and C:P ratios were significantly higher in Pinus than in the Robinia plantations, but the N:P ratio in Pinus was less than that in the Robinia plantation. 2) The litter N and P concentrations were significantly higher in Robinia than in the Pinus plantations, but the C concentration was significantly lower in Robinia than in the Pinus plantations. In addition, the litter C:N ratio was higher in Pinus (70.21) than in the Robinia (19.71) plantations. This indicated that the lower decomposition rate of litter was advantageous to nutrient storage in the Pinus plantation. 3) The soil C and N concentrations decreased with increasing soil depth, but the P concentrations remained constant in both plantations. The soil C concentration in Robinia was less than that in the Pinus plantation, but no difference was observed in N and P concentrations. 4) The correlations between the C, N, P, and nutrient ratios of the arbor leaf, shrub leaf, herb leaf, litter, and soil in the Robinia plantation were more focused in the 10-20, and 20-30cm soil layers, and these correlations in the Pinus plantation were relatively lower, with no significant correlation even in 20-30cm soil layer. This indicated that compared with the Robinia plantation, the supply of N and P had no significant impact on the N and P content of leaf in the Pinus plantation. This study establishes the foundation for illuminating the ecosystem nutrient coupling mechanism in Loess hilly-gully region, as well as provides a guiding significance for the vegetation restoration in the Loess hilly-gully region.