The distribution of particle size segregation is an inevitable phenomenon during the burden distribution process of blast furnace, which can easily lead to the decrease of porosity and the increase of pressure at the throat of the furnace top. As a result, it makes an indirect impact on the uniform distribution of gas flow, thus indirectly affecting the smooth operation of blast furnace. Based on DEM (discrete element method)simulation method, present work studies the segregation status of binary particle mixtures and proposes a segregation index T, which could be used to characterize the relative degree of particle size segregation distribution. The results show that: in the same T value graph, the greater of the difference of value T between the adjacent area is, the greater of the degree of particle size segregation of the above areas is; and in different T value graphs, the greater of the average of all the absolute difference of value T between adjacent areas is, the greater of the overall degree of particle size segregation is.