Abstract: Bentonite, a major binder in the pellet ore production process, can significantly improve the sphericity of raw materials and enhance pellet quality, but the higher SiO2 and Al2O3 content will cause an increase in the slag volume of ironmaking production. The addition of a minor amount of organic binder to replace part of the bentonite is essential to improve the pellet performance. In this paper, the effect of organic binder P replacing part of bentonite on the high temperature strength of pellets was investigated. Laser flash method and TG thermogravimetric method were employed to investigate the effects of organic binder on the internal structure, heat transfer and mass transfer of pellets. The results indicated that the composite binder could replace part of the bentonite and significantly improve the strength of preheated and roasted pellets with the increase of the addition. The organic binder P was pyrolyzed at high temperature and formed pores inside the pellet, resulting in lower thermal conductivity of the pellets, slower internal heating gradient. The formation of a dense oxide layer on the surface of the pellets due to rapid oxidation was avoided. Meanwhile, the tiny pores facilitated oxygen transfer to the interior of the pellets and promoted the oxidation of Fe3O4 to Fe2O3. The oxidation fraction fTGA gradually increased from 90.80% to 92.17% with the addition of organic binder P.