Abstract: Four land use types of cropland, abandoned cropland, 10-year-old and 43-year-old Robinia psedudoacia plantations in the Grain-for-Green Program in hilly area of North China were studied to investigate the effects of returning cropland to forestland on soil quality by using integrated soil quality index. The results showed that the nutrients of topsoil increased significantly with increasing tree age, and soil properties in 0-5 cm soil layer improved. Compared with the cropland, soil physical and chemical properties of the two R. psedudoacia plantations improved, and the soil microbial biomass C and N increased significantly. The integrated soil quality index decreased in order of 43-year-old R. psedudoacia plantation (0.542) > 10-year-old R. psedudoacia plantation (0. 536)> the abandoned cropland (0.499) > the cropland (0.498), suggesting the soil quality was improved during the conversion from cropland to forestland.