The kinetics of pyrolysis of black liquor was studied via thermogravimetric analysis of 10℃/min,20℃/min,40℃/min,50℃/min with Zsoko method.The results show that the process of kinetics consists of 4 stages,three of which have obvious weight loss peaks and the third stage has a weight-loss platform.Because the kinetics of pyrolysis is complicated,each temperature stage was taken as independent object to describe the pyrolysis behavior with different mechnism functions.In the stage of 150~450℃ pyrolysis of organic phase,the activation energy goes down with the increase of heating rates and the water content.