Abstract: Iron rod method was adopted for industrial metal flow measurement of six aluminum reduction cells. 300 kA and 400 kA cells with same and different height of cathode blocks, end cell and middle cells were analyzed. The characteristics of whole horizontal flow and regional vertical flow in liquid aluminum were investigated by analyzing the phenomenon of different measured iron rods, which show normal erosion, thick-thin-thick character, turned eroded surface, numerous eroded holes. The flow velocity of the cells with different cathode structures was compared. In the direction of cell length, there are four eddies with big-small-small-big state in same height of cathode blocks 400 kA cell and two homogeneous eddies in different height of cathode blocks 400 kA cell, while there are five homogeneous eddies in same height of cathode blocks 300 kA cell.