The invention discloses a CO2 capture device of an internal combustion engine, which comprises a casing, an inlet (1), a dry ice falling block (2), an outlet (3), a liquid oxygen spray device (4), a convective heat transfer chamber (5), a dry ice falling track (6), and a dry ice collector (7). The internal combustion engine exhaust CO2 is captured, and the liquid oxygen is vaporized to oxygen gas which enters the internal combustion engine together with non-sublimated CO2 to realize oxygen enriched combustion; meanwhile, the generation of NOx and CH and CO is eliminated. The liquid oxygen is introduced into the device and vaporized under heat, the exhaust CO2 releases heat and sublimates to dry ice, and the rest CO2 and vaporized oxygen gas enter the internal combustion engine to carry out oxygen enriched combustion, so that the internal combustion engine realizes zero discharge. The device disclosed by the invention can be used together with the internal combustion engine to enable the internal combustion engine to operate in a narrow space requiring zero discharge, such as military tunnel construction vehicles, tunneling machines, well drilling generators, submarine generators, military missile launching vehicles and other occasions. The dry ice recovered by the device can be reused, and can be sued for refrigeration, dry ice cleaning agents, plant nutrients and the like.