Abstract: With urban population growth and rapid urbanization, a large amount of sewage sludge and green waste are produced every day. The application of mixed composting products from anaerobic digested sludge and green waste for soil amendment in woodland is an economical and effective way for the re-use of urban waste. In this study, an experiment was conducted in Beijing Plain afforestation area to explore the effects of mixed compost application on the growth of Cosmos bipinnatus and its absorption of heavy metal elements. Results showed that application of compost had no significant effect on the contents of total soil N and organic matter. Meanwhile, three heavy metals, i.e., Cu, Zn, and Cd, were mainly present as residual form in the soil. Although compost application increased the Cu and Zn contents in soil, total Zn content did not exceed the pollution risk screening value of 300 mg·kg^-1 by the Soil Environmental Quality Standard of China (GB 15618-2018), while total Cu content exceeded the pollution risk screening value of 100 mg·kg^-1 only when the dosage of compost was high. Cd content in the ambient soil had exceeded the value of soil pollution risk control value of 4.0 mg·kg^-1. There was no effect of compost application on the Cd content. Plant height, biomass, and flower number of C. bipinnatus increased with the increasing compost dosage. The enrichment capacities of C. bipinnatus to the three heavy metals were in order of Cu>Cd>Zn. Our results demonstrated that plantation ecosystems in Beijing plain region could tolerate certain concentration of heavy metals from the mixed compost, and utilize other nutrients to improve the soil fertility with positive effect on plant growth.