The particle size and distribution of some granulated blast furnace slag powders ground by vertical mill and ball mill were analyzed using laser particle size analyzer.The results indicated that the particle size distributions of the granulated blast furnace slag powders obtained by these two kinds of milling processes all accorded with RRSB equations;n value can exactly reflect the level of the particle size distribution range of powder;the particle size distribution range of the slag powder ground by ball mill was wider than one of the slag powder ground by vertical mill;compared with Fulller curve,the contents of fine particle and coarse particle was less,but the content of middle particle was more.The numerical values of contents of fine and coarse particles in the slag powder ground by vertical mill was more far from Fuller curve than one of the slag powder ground by ball ball;in the particle characterization parameters,The general coarse-fine grade of the two kinds of ground slag powder can be accurately characterized with both specific surface and median diameter(d50).