Abstract: With the depletion of free-milling mineral resources with coarse dissemination size, dealing with the fine-dissemination-size mineral resources becomes an inevitable trend. Fine grinding is an indispensable pathway in efficient utilizing of micro granular mineral resources. Horizontal stirring mill is a new effective fine grinding equipment and has a widely industrial application. However, the running processes of the equipment is affected by a lot of factors and it is difficult to control the particle size distribution of grinding products. In this paper, the rougher concentrate which is obtained from magnetic separation process of Gongchangling Concentrator of Ansteel Mining is take as a research object. The particle size distribution equations, such as GGS, RRB, and S, are employed in this study to investigate the particle size distribution of grinding products of horizontal stirring mill. Meanwhile, the effect of feed rate, blender speed, pulp density, and medium filling rate on particle size distribution characteristics of grinding products is researched in this study. The findings show that RRB is the best fitting equation to analysis the particle size distribution of griding product of horizontal stirring mill. There is a negative correlation between uniformity index of grinding products and feed rate. With the improvement of blender speed and pulp density, the uniformity index of grinding products first increases and then decreases. There is a positive correlation between uniformity index of grinding products and medium filling rate. According to the results of orthogonal experiment, the effect of the factors on the equality of the grinding products follower the order of feed rate＞blender speed＞pulp density＞medium filling rate. A uniformity index of grinding products of 0.965 is obtained under the optimal condition: feed rate of 12 kg/h, blender speed of 1 500 rpm, pulp density of 30%, and medium filling rate of 70%. The research results provide a theoretical basis for optimizing the control of particle size distribution in the grinding products of horizontal stirring mills.