This study is aimed to describe the influence of different factors on the leaching process of heavy metals from urban sewage sludge, which was mainly based on the establishment of hazard-free treatment strategy of sewage sludge and a framework of marine environment protection. The modified horizontal extraction procedure was adopted to explore the impact of temperature, salinity and microbial activity on the leaching of sewage sludge-associated heavy metals collected from seven typical waste water treatment plants (WWTPs) in Shanghai. The results indicated that the releasing of dominated heavy metals from sludge were Zn and Hg under higher temperature, and Cu, Cd, Pb and As were the dominated ones under lower temperature; Salinity in seawater could affect the electrolyte concentration and activity of some enzymes, which led to Zn, Cu, Pb and Cd tend to be released in sea water at lower salinity. Many microbial activities such as oxidation reaction, nitrification and so on could affect the speciation and characteristics of heavy metals in sewage sludge, and more Zn, Cu, Hg and As would be released after sewage sludge were sterilized.