In order to fully oxidize and reduce the inner layer of pelleting and improve the compressive strength of pellets, the mixture of magnetite and hematite is used as raw materials to carbonate the inner layer of pelleting. And then the carbon is pelletized, dried, preheated and roasted to study the influence of the ratio of inner diameter, alkalinity, hematite and magnetite on the compressive strength of pelleting. The results show that the compressive strength of pellets increases and then decreases with the increase of inner diameter, and the average compressive strength of pellets is 3 265 N/P when the inner diameter is 6~8 mm; the compressive strength of pelleting increases and then decreases with the increase of proportion, and the compressive strength of pellets is maximum when the ratio of hematite and magnetite is 3:7; the compressive strength of pellets gradually increases with the increase of alkalinity. The highest compressive strength of the finished pellets is 3 319 N/P when the inner diameter of pelleting is 6 to 8 mm, the ratio of hematite to magnetite is 3:7 and the alkalinity is 1.0.