In this study, a field experiment was conducted to determine the effects of sewage sludge biochar (SSBC) on poplar-planting soil physicochemical properties, heavy metal contents, microbial biomass carbon and nitrogen contents and enzyme activities. Four SSBC treatments were designed: CK (0 t/hm²), LS (15 t/hm²), MS (30 t/hm²) and HS (60 t/hm²). The results showed that SSBC treatments decreased soil pH and enhanced soil electric conductivity. The contents of soil nutrients and heavy metals were increased with the increase of SSBC, in which, soil organic carbon increased by 18.4%–47.9%, total nitrogen by 20.4%–46.5%, total phosphorus by 27.9%–74.9%, available nitrogen by 4.2%–23.1% and available phosphorus by 16.3%–28.3%, respectively. Moreover, the heavy metal pollution was controllable. SSBC enhanced the contents of microbial biomass carbon and nitrogen and significantly increased the activities of β-glucosidase, N-acetyl-glucosidaseand protease by 17.1%–35.3%, 18.1%–36.8% and 29.3%–70.3%, respectively, in which, MS treatment increased the most. In conclusion, SSBC application not only significantly improves soil nutrients, but also improves microbial environment, thus, improves soil environmental quality in a certain degree.