Experimental studies were carried out on surface area of char during pyrolysis of sewage sludge. To evaluate surface area of resultant char we use iodine number. Increase of iodine number shows that the surface area of char increases. The process parameters, temperature and holding time have significant effect on surface area of char. Increasing temperature above 400℃ surface area of char decreases while slightly increasing when holding time increases. In this study, the optimum conditions for high surface area of resultant char were found 400℃ and 30minutes, respectively.