The homeostasis characteristics of plants and microbes during vegetation restoration are important indicators of the ability of organisms to adapt to environmental changes and also provide insights into ecosystem nutrient cycling. The aim of the present study was to investigate the C, N, and P contents and ecological stoichiometric ratios (leaves, soil, and soil microbial biomass) of five Robinia pseudoacacia forests in the Loess Hilly Region of China, selected based on their restoration ages (i.e., 5, 10, 20, 30, and 45 years). The homeostasis characteristics of leaves and soil microbial biomass along with stand ages were emphatically revealed. Each of the forest included three replicate lands. Each replicate land included three sample plots (20 m×20 m), and soil samples were collected from five points in each plot by using a soil auger (4 cm diameter), before being homogenized and analyzed. Leaves samples were collected from 10 individual trees in each sample plot. Vegetation surveys included five randomly selected plots (1 m×1 m) at each site. The results showed that:(1) The C and N contents of the leaves, soil, and soil microbial biomass all increased with recovery duration (P < 0.01), and the P contents increased, although not significantly. (2) The C ∶ N ratios of the leaves, soil, and microbial biomass were 17.03-26.03, 9.55-16.94, and 5.57-10.76, respectively, whereas the C ∶ P ratios were 465.04-634.48, 19.89-65.81, and 39.64-110.53, and the N ∶ P ratios were 17.89-37.03, 1.24-4.68, and 7.15-10.26, respectively. All stoichiometric characteristic ratios showed mostly increase trends with the increase of the recovery age, except for the leaf C ∶ N was decreased (P < 0.01). (3) The relationships between C, N, and P contents and their ratios in the leaves and microbial biomass with corresponding soil parameters can be adequately simulated using an internal homeostasis model (P < 0.01). Only leaf N ∶ P and microbe C and N contents were sensitive to changes in the soil nutrient contents. These results indicate that plants and microbes reach homeostasis by self-regulation, regardless of soil nutrient changes, thereby suggesting that R. pseudoacacia forests in the Loess Hilly Region are well adapted to environmental change. However, compared to plants, soil microbes were more sensitive to environmental changes, indicating that soil microbial biomass nutrient content can be used as an indicator of soil restoration status in R. pseudoacacia forests.