The sewage sludges were collected from three municipal sewage treatment plants in Nanjing, Danyang, and Ma Anshan and then the pyrolyzed wastewater sludges were prepared at 500℃. The properties of the wastewater sludges and pyrolyzed wastewater sludges were measured, and their ameliorating effects on the acidity of a red soil and the environmental risk of application of the pyrolyzed wastewater sludges were investigated. The results indicated that incorporation of pyrolyzed wastewater sludges increased soil pH and soil exchangeable Ca2+, Mg2+ and K+ and decreased soil exchangeable acidity due to the alkalinity of the pyrolyzed sludges. However, the strong nitrification occurred due to large amount of ammonium presented in the sludges when the sludges were incorporated into the soil, which produced the large numbers of protons and offset the ameliorating effects of the sludges on the acidified red soil. The incorporation of the sluges and pyrolyzed sluges increased the contents of soil organic carbon, available phosphorus and readily available potassium and thus improved soil fertility. The pyrolyzation of the sluges led to the increase of the total amount of heavy metals in the sluges, while the contents of the available species of most heavy metals in the sluges were decreased, which suggested that the pyrolyzation of the sluges decreased the activity of most heavy metals in the sluges. Compared with control, the incorporation of the pyrolyzed sludges increased the available species of some heavy metals in the soil, and the content of the available Zn increased obviously. Therefore, there is the potential environmental risk for the pyrolyzed wastewater sludges used in agricultural soils. It is a better choice to use the pyrolyzed wastewater sludges to correct the acidity of the forest soils.