Biochar produced from sewage sludge could provide an important alternative to waste management practices while offering an opportunity to improve soil properties and reduce the risk of contamination from direct applications of sewage sludge soil amendments. We assessed the impacts of different rates of biochar application (20, 40, 60 t ha^-1) to peanuts grown in a loamy sand soil in the North China Plain on composition of the soil microbial community, soil bulk density (BD), pH, total carbon (TC), total nitrogen (TN), C:N, available phosphorus (P), available potassium (K), dissolved organic carbon (DOC) and crop yield. We found that sewage sludge biochar application increased TC, TN, available K, and C:N, and decreased soil BD and pH and had variable effects on DOC. Amendment with biochar increased microbial biomass and the proportion of Gram-positive bacteria, Gram-negative bacteria, fungi and Actinomycetes, while it decreased the ratios of groups of bacteria. The highest crop yield was achieved under 40 t ha^-1 of biochar. Our study suggests that the lower rates of sewage sludge biochar application could improve soil physicochemical properties and increase levels of soil microbes and crop yield; however, the highest rate may induce negative effects on microbe community composition.