Abstract: The influence of the factors,including the processing capacity of raw ore,the concentration for the autogenous mill,ball milling density,graded overflow thickness and the grade of iron ore,on the qualified rate of the fineness of iron concentrate powder is studied in this paper.The investigation is based on the production data obtained in one Anhui dressing plant in April of 2013.In view of our analysis,we find that the fineness of the iron concentrate powder is little affected by the processing capacity of raw ore,concentration for the autogenous mill and ball milling density.However,the graded overflow thickness and the grade of iron ore have large effect on it.Specifically,the fineness of the iron concentrate powder will be reduced with the increase of the graded overflow thickness and the grade of iron ore.