The results show that exergy analysis could more profoundly and more scientifically reflect the essence of energy than energy analysis,more really reflects the transformation and loss situation of the quantity and quality of energy,also indicates a direction for the system to save energy.The two methods of the thermal dynamic analysis are compared.Through thermal balance and exergy balance calculated on the system of precalcination kiln in Wulan,the reasons causing exergy loss and the degree to which they affect the efficiency are analyzed.The weak links in the system are confirmed,and many ways are found to save energy.It can also be pointed out that waste heat generation is the best way to decrease exergy loss at this time.