The reduction of iron ore-coal composite pellets was carried out in the temperature range of 500～ 1200°C by thermogravimetry. This study aims to investigate the effect of particle size of iron ore on reduction behavior. Three samples of different particle size were selected: 25～48μm, 75～106μm and 150～180μm. The reaction kinetic parameters were estimated based on the thermogravimetric data. The characterization of the heated residues was identified by X-ray diffraction and Scanning electron microscope. The experimental results indicated that the selected iron ore with particle size 25～48μm was appropriate for the reduction of iron ore-coal composite pellets in the experimental conditions, and particle size 75～106μm and 150～180μm were insufficient to complete the reduction. With the increase of particle size, the activation energy increased from 53.04kJ/mol to 131.72kJ/mol. Particle size 25 ～48μm had the faster reduction which may be ascribed to more developed surface.