In order to utilize the limestone sludge of limestone calcination plant as a by-product, present study had been performed to estimate the usability of limestone sludge as a raw material of sinter mixture in iron ore sintering process and the influence of addition of limestone slurry and dried limestone sludge on the sintering properties. The results of sintering pot tests showed that limestone sludges might be used in iron ore sintering process in the phase of slurry and dried powder without the deterioration of sinter quality. The optimum density of limestone slurry and ratio of sludge to sinter mixture were 20% and 1.2%, respectively. In the respect of sinter quality, strength(TI) and reduction index(RI) was decreased with the increase of limestone sludge containing dolomite particles due to the decrease of calcium ferrite and the increase of low reducible magnetite of sinter.