In recent years, co-processing lime-dried sludge (LS) in cement kilns has attracted increasing interest in China. However, there are few published studies focused on the effect of sludge properties. In this study, LS properties and their effects on co-processing in a cement kiln were studied by performing experimental analyses and theoretical calculations. The results indicated that the heating value of municipal sewage sludge (MSS) was decreased with lime dosage. By adding 10% lime, the heating value would be almost halved to 7,198 kJ/kg. Heavy metals in LS are much lower than the limit concentration of the standard. Chlorine and sulfur are about 0.06-0.35% and 0.22-0.56%, respectively, which completely meets the relation requirement. Additionally, adding lime promotes the transformation and decomposition of ammonia and protonated amine proteins, nitrogen, and the generation of pyridine nitrogen. Theoretical calculation results show that the maximum co-processing ratio for RS is 4.5%, which can be increased by increasing the addition of a suitable amount of lime (0-16%). 10% with a 6.5% maximum co-processing ratio is suggested as the optimum lime dosage for co-combustion of LS in cement kilns.