In order to reduce the production cost of iron ore pellets drying process，accelerate the pelletization speed， promote the formation of large pellets，and improve the comprehensive performance of pellets，the pellets in the range of 10 ~ 12，12 ~ 14，14 ~ 16 mm and 16 ~ 18 mm are taken as the research objects to explore the influence of particle size on pellets performance and process conditions. The results show that increasing the particle size of the pellets requires higher pelletizing moisture and longer pelletizing time，and the falling strength and compressive strength of the fresh pellets are significantly improved. With the increase of pellets size，the arrangement of particles inside the preheating pellets is more regular，the proportion of solid phase inside the finished pellets increases，the porosity decreases，the crystal connection is better，the compactness is improved，and the compressive strength of the preheating pellets and the finished pellets increases. The particle size of pellets should not be higher than 16 mm，when the particle size is increased to 16 ~ 18 mm， the reduction expansion index decreases from 11. 6% to 9. 7% ，and the reduction index decreases from 70. 7% to 54. 5% ，and the reduction degree becomes worse. Mild drying or non-drying of iron ore concentrate can help to improve the particle size of pellets，greatly reduce the proportion of ＜ 12 mm particle size in fresh pellets，increase the proportion of 12 ~ 16 mm particle size，and make the particle size distribution of green pellets more uniform. Therefore，controlling the particle size at 12 ~ 16 mm in pellets production can not only save drying costs，but also obtain better pellets performance indexes，and provide more high-quality charges for subsequent blast furnace smelting.