The invention relates to a device for cooling an erodible part of a flat glass melting furnace tank wall. A circulating cooling device using tin liquor as a medium is arranged at the erodible part between a tank wall (11) and a seam brick (3); the circulating cooling device comprises a cooling box (1) between the tank wall (11) and the seam brick (3); a tin liquor outflow pipe (5) and a return pipe (10) are respectively arranged at the upper and lower parts of one side of the cooling box (1); the end parts of the outflow pipe (5) and the return pipe (10) are connected with a spiral cooling pipe (8); a tin feeding opening (6) is formed in the outflow pipe (5); a re-cooling air pipe (7) is additionally arranged on the outflow pipe (5) to contain the spiral cooling pipe (8); a temperature sensor (4) is arranged on the outflow pipe (5). The device disclosed by the invention has the advantages as follows: the tin liquor is used as a coolant, and heat-resistant steel is used as a component so as to ensure that the temperature of a cooling part is controlled to be 1000-1100 DEG C; the heat exhausted by cooling can be greatly reduced; the economic benefits generated by prolonging the service life of a melting furnace are much greater than the lost economic benefits caused by the increase of the energy consumption.