The invention belongs to the technical field of pig casting machines for continuously producing casting pigs, and in particular relates to an iron alloy grain casting machine, which consists of a chain type slope conveyor, a grain casting die, a slurry spraying mechanism, a water cooling mechanism, a shocking device, an iron alloy liquid pouring insulation chute, a finished grain casting product receiving hopper and an electric control device, wherein the chain type slope conveyer consists of a conveyor frame, a chain inclined rail, a conveyor driving device, a conveyor tensioning and rotating device, and an annular roller chain; the slurry spraying mechanism consists of a stirring device, a slurry spraying stirring tank, a slurry spraying tank, a coating slurry sprayer and a slurry return groove; the water cooling mechanism consists of a water sedimentation tank, a water cooling tank connected with the water sedimentation tank through a water connecting pipe, a cold water sprayer and a water return groove; and the shocking device consists of a shocking bracket, a shocking driving device, an eccentric block, a fixed pin roll, a connecting rod, a reciprocating rod, a guide sleeve, a spring and a contact. The iron alloy grain casting machine completes a series of work procedures such as pouring, cooling, demolding and collecting iron alloy grains at one time and reduces labor intensity and production cost.