The utility model relates to a preheating zone furnace gas after burner of a cupola furnace, which comprises an air intake main pipe, an exhaust pipe, a bustle pipe and a branch air pipe, wherein the bustle pipe is enclosed on the outer side of the cupola furnace, the lower end of the bustle pipe is connected with the air intake main pipe, a control valve is arranged on the air intake main pipe, the side surface of the air intake main pipe behind the control valve is connected with the exhaust pipe, an exhaust valve is arranged on the exhaust pipe, the inner side of the bustle pipe is communicated with the branch air pipe, and the front end of the branch air pipe extends into the air port of the cupola furnace. The preheating zone furnace gas after burner of the cupola furnace has the advantages of reasonable design, small size, convenient operation and obvious energy-saving effect; and is widely applied in various cupola furnaces.