Ecological stoichiometry is an effective method to study the element balance and energy flow of ecosystem. Defining the stoichiometry characteristics of plants and soil under different vegetation types is of great significance to reveal the nutrient cycling of ecosystem in the process of vegetation restoration on the Loess Plateau. It can provide a feasible basis for the selection of vegetation restoration types on the Loess Plateau. In this study, five vegetation types (Stipa bungeana grassland, Leymus secalinus grassland, Medicago sativa grassland, Caragana korshinskii shrub, and Armeniaca sibirica forest) under three vegetation restoration methods (natural grassland, natural restoration and artificial restoration) in the semi-arid loess small watershed were selected as research objects. The carbon (C), nitrogen (N), phosphorus (P) concentrations and ecological stoichiometry characteristics of leaves, stems, roots and soil under different vegetation types were analyzed. The results showed that: 1) plant organs and vegetation types had significant effects on plant ecological stoichiometry characteristics. The concentrations of C, N and P in five vegetation types were leaf > stem > root. The concentrations of C, N and N:P in all organs of the artificial restoration vegetation were significantly higher than those in the natural grassland. There was no significant difference between the artificial restoration vegetation and the natural restoration vegetation. Among them, C concentration in all organs of A. sibirica and N concentration in all organs of C. korshinskii were the highest in artificial restoration vegetation. The C:N of natural restoration vegetation was significantly higher than that of artificial restoration vegetation and natural grassland. The concentration of P and C:P had no significant difference among different vegetation types. 2) There were some differences in soil ecological stoichiometry characteristics under different vegetation types. The concentrations of C, N, P, C:P, and N:P in artificial restoration vegetation soil were the highest, significantly higher than those in natural restoration vegetation soil. The C, N concentrations and C:P, N:P of C. korshinskii soil in artificial restoration vegetation were significantly higher than those of other vegetation soils. There was no significant difference in soil P concentration and C:N between five vegetation types. 3) The correlation of C, N and P concentrations between plant leaves and soil was different under different vegetation types, which indicated that plant growth characteristics affected the transformation and transfer of nutrients between plant and soil. In conclusion, the ecological stoichiometry characteristics of leaves, stems and roots of vegetation showed a significantly positive correlation with each other. Between plant and soil, there was a significantly positive correlation between plant N concentration and soil C, N, P concentrations, and a significantly positive correlation between plant N:P and soil N:P, indicating that the changes of ecological stoichiometry characteristics of plant and soil in the Loess small watershed ecosystem were restricted and influenced each other.