In this work, the sequential SO2 and CO2 capture behavior of lime mud (LM) as a solid waste from the paper industry was investigated in the calcium looping process. In order to minimize the unfavorable effects of impurities such as Na and Cl on CO2 and SO2 capture of LM, the LM was prewashed with distilled water. The prewash treatment improves the cyclic CO2 capture capacity of the LM during multiple carbonation/calcination cycles. The ultimate carbonation conversion of the treated LM is 1.8 and 4.8 times greater than those of the raw LM and the limestone, respectively. The microstructure analysis shows that the surface area and pore volume of the LM are significantly increased after the prewash treatment. With increasing the sulfation temperature from 850 to 950 degrees C, both the raw LM and the treated one show an increase in the sulfation conversion after the same number of cycles. Interestingly, the effect of the sulfation temperature decreases with increasing the number of cycles. For the raw LM or the treated LM, the sulfation conversion after 50 cycles is higher than that after 15 or 100 cycles. That is related to the change in pore size of the raw LM and the treated LM after multiple cycles. Compared with the raw LM and the limestone, the sulfation conversion of the treated LM is greater after the same number of cycles and at the same reaction time.