In order to improve the quality of fluxed pellets and analyze the variation law of pellets properties under different particle sizes,the pellets production line of belt roaster in new area of Tangshan iron and steel is taken as the research object,and the metallurgical properties and mineral phase structure of pellets under such four particle sizes as 8.0～10.0,10.0～12.5,12.5～16.0 and 16.0～20.0 mm are studied by means of cage pelletizing test and metallurgical performance testing,respectively.The results show that,with the gradual increase of the particle size of the fluxed pellets,the compressive strength of the pellets is increased from 1 767 N/P to 3 606 N/P,the reduction degree is decreased from 78.5% to 47.8% at 1 h,the reduction expansion index is decreased slightly,remaining below 12%,the low?temperature reduction pulverization(＞6.3 mm) is decreased from 87.8% to 66.5%,the low?temperature reduction pulverization(＞3.15 mm) is decreased from 95% to 87.2%,and the low?temperature reduction pulverization(＜0.5 mm) is changed slightly,about 4%. With the gradual increase of the particle size of the fluxed pellets,the porosity is decreased,from 38.93% to 31.4%,the liquid phase ratio is decreased slightly,and the solid phase ratio is increased significantly,from 41.05% to 58.41%. The density is increased but the decrease of liquid phase rate may make the existing link state ineffective,and the low?temperature reduction and pulverization performance of fluxed pellets is weakened.Therefore,in the production process of fluxed pellets,the appropriate particle size of pellets should be controlled to improve the properties and microstructure of fluxed pellets,which is conducive to the smoothly increasing output of blast furnace.