Due to continuous global population growth and consequently unprecedented increase in human's daily demands on food and other consumption materials, the production of a large volume of different types of waste water and sewers and in particular sewage sludges are inevitable which necessitates more attention and efforts to propose new and efficient treatment and removal of such wastes from environment. The conventional and commonly used methods for removing sewage sludge such as deploying directly in agricultural fertilizers or disposing through landfilling are not only capable of resolving the issue but also have produced more pollution and environmental problems. In recent years, there has been an increased interest in using thermal processing of wastes to avoid such damages to environment. In current study, the urban sewage sludge was used as input material to the pyrolysis process to produce biochar at different temperatures namely 300, 400 and 500 ° C. The biological factors affecting the biochar production, including pyrolysis efficiency, pH, and percentage of the surface area were investigated. In order to study the capability of biochar in stabilizing contaminated soils, the produced biochar outputs from pyrolysis process at temperatures of 300, 400 and 500 ° C, were added at mass ratios of 1, 3 and 5 percents to a known highly contaminated with heavy metals soil. The contaminated soil was taken from Bama Zn/Pb mine located in about 15 kms South East of Esfahan city, having 194 and 1640 mg/kg lead and zinc respectively. Next, the soil samples mixed with biochar in different portions were kept in the laboratory for different time durations (including 15, 30, 45, and 60 days) for analyzing the ability of biochar in stabilizing soil contamination. For analyzing the results, Design Expert 10.0.3 software was used. The experiment design algorithm proposed 20 tests to assess bioavailability of lead and zinc metals, out of which 5 experiments were duplicate. Then, the bioavailability of lead and zinc was determined using a Perkin-Elmer atomic absorption spectrophotometer (AAnalyst700) through DTPA sample pre-processing and preparation. In general, the results show meaningful correlation between biochar pyrolysis temperature and samples pH. According to the results, increasing the pyrolysis temperature from 300 to 400 °C, results in increased carbon enrichment, but moving from 400 ° to 500 °C, the concentration of carbon is decreased. The performance of producing biochar using pyrolysis procedure explained above, is greatly influenced by temperature so that up to 300 °C the recovery is 91% but increasing the temperature to 500 °C it drops to 71%. Although increasing the temperature of pyrolysis process has improved lead stabilization to 58 wt. % in the soil but the zinc concentration was stabilized at about 51 wt%. Also, the effects of three major factors on bio-availability of metals in contaminated soil including different types of carbon (pyrolysis temperature), the percentage of mixing and incubation time, were investigated. The influence of biochar type on bioavailability of metals was less than other two factors namely mixing and incubation time. By increasing the proportion of biochar in contaminated soil, zinc stabilization is increased, whereas this behavior is reversed for lead stabilization. Also, it is found that increasing incubation time, would result in increasing percentage of lead and zinc stabilization meaning the effectiveness of using biochar in stabilizing contaminated soils in long term environmental cleanliness activities. Finally, we can conclude that using biochar products as the output of pyrolysis of sewage sludge for stabilizing heavy metals in contaminated soils is not only an effective approach but also would contribute to reduce the risk of entering these heavy metals in groundwater resources which would in turn result in establishing more sustainable environment and long term stability. Key Words : Sewage sludge, heavy metals, contaminated soil, Biochar, pyrolysis.