The utility model provides a residual iron recycling system for an iron making plant torpedo tank car. The residual iron recycling system comprises the torpedo tank car and a pig-casting machine, wherein the pig-casting machine comprises a revolving chain belt and an iron mold arranged on the revolving chain belt; a smoke dust collecting structure is arranged over the torpedo tank car; an iron slag switching device is arranged under the torpedo tank car; a slag car is arranged under the iron slag switching device; the running direction of the iron slag switching device is parallel to the running direction of the pig-casting machine; the running direction of the slag car is vertical to the running direction of the pig-casting machine; a steam collecting device is arranged correspondingly above the pig-casting machine along the running direction of the pig-casting machine; a pig iron guide chute, an iron peeling device, a pulping and spouting device and a spray cooling device are arranged below the pig-casting machine in sequence from top to bottom. By adopting the system, residual iron in the torpedo tank car can be reasonably recycled into pig iron according to a subsequent procedure standard, and high quality stability and continuity of pig iron are ensured.