<p>Limestone was pretreated via the mechanical activation method, and burnt lime was partially substituted by the pretreated limestone for better sinter indices and lower sintering costs. With the reduction in the size distribution of the pretreated limestone, the particle morphology, the activity of the calcined limestone and the fluidity of the liquid phase during sintering are all improved. When the substitution ratio of the pretreated limestone for burnt lime is kept at 50%, the granulation performance and sinter indices in sinter pot tests are both better compared with that of the base case. Much denser interleaved texture in product sinter is formed with the reduction of sinter porosity and improvement of silico-ferrite of calcium and alumina amount. When the particle size of the pretreated limestone is maintained within the optimal range of 0–2 mm, the tumble index, yield and productivity increase by 7.2%, 2.6% and 11.2%, respectively, while the solid fuel rate decreases by 8.7%. In the corresponding sinter industry production, the tumble index and output of the product sinter are comparable to those of the base case, while the coke dosage is reduced by 9.0%. Reduction index and reduction degradation index (RDI_+3.15) are both higher than 74%. The cost of raw materials in sintering process can be greatly reduced.</p>