The municipal wastewater biology treatment process includes both pollutants transferring and energy utilization. The wastewater and sludge samples of several WWTP (wastewater treatment plant) in Chongqing are investigated. The heat value, volatile component and element content of those samples are determined. The effect of volatile component on heat value is analyzed. The results show that it has a good correlation between volatile component and heat value. The heat value has a negative correlation with volatile component when volatile component is below 30%, while it has a positive correlation with volatile component when volatile component is above 37%. The heat value is also calculated by the Dulong formula. The conclusions are pretty close: heat value has a negative correlation with volatile component when volatile component is below 28.26%, while has a positive correlation with it when volatile component is above 28.26%. It indicates that the analysis method for heat value of wastewater and sludge in this paper is effective, and it can be used in wastewater measurement.