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.