The transitional behavior of burden and gas distribution in the blast furnace was studied aerodynamically by a blast furnace model. When ore is charged under a gas flow, a coke column (hereinafter referred to as the central coke column) forms in the central region. On the basis of the experimental observation, the formation process of the column consists of the following three steps.(1) With the progressive covering of the stack surface by the flow of ore from the periphery to the center, the furnace gas concentrates to the central region.(2) The coke layer expands upward in the region where the gas velocity exceeds the minimum fluidization velocity of the coke layer.(3) Some of the coke lump in the expanded layer are pushed into the central part by the flow of charged ore.The central coke column is formed more easily by pellet charging rather than by sinter charging. The gas velocity in the central part has been related to the thickness and area of ore layer and the permeability ratio of ore to coke, and it has been expressed by the following equations. UC/UT=1/{AC/AT+(AW/AT)/(UC/UW)} UC/UW=C0{(H/R)•(k1/k2)0.778(AC/AT)-0.483}n where, A is the sectional area, U, the gas velocity, H, the ore thickness, R, the throat radius, K1 and K2, the permeability indices of coke and ore, respectively, C0 and n, constants, suffix C and W, the central region without ore and the peripheral region covered with ore, respectively, and suffix T, the throat. The radius of central coke column has been estimated from three relations to be about 0.58m.The pressure drop in the stack of blast furnace is decreased by the formation of a central coke column, while the distribution of gas through the coke layers in the softening-melting zone hardly changes.