A low-temperature abrasive jet machining device is characterized by comprising an abrasive jet generation system, a cooling system and a machining system. The abrasive jet generation system mainly comprises a nitrogen cylinder (1), a grinding bin (2), a gas-powder mixing device (15), an abrasive jet pipe (8) and an abrasive jet nozzle (14). The cooling system mainly comprises a self-pressurizing liquid nitrogen container (5), a liquid nitrogen safe valve (4) and a cooling pipe (16); and one end of the cooling pipe (16) is connected with the self-pressurizing liquid nitrogen container (5) through the liquid nitrogen safe valve (4), and the other end of the cooling pipe (16) is connected with a composite nozzle (11). The abrasive jet pipe (8) and the abrasive jet nozzle (14) connected with the abrasive jet pipe (8) are both installed in the cooling pipe (16) so as to achieve cooling in the flowing process of abrasives, and while the abrasives are ejected out of the abrasive jet nozzle (14), the abrasives are mixed with low-temperature nitrogen entering the composite nozzle (11) through the cooling pipe (16) and then are ejected to a workpiece (13) through an ejection port of the composite nozzle (11). According to the low-temperature abrasive jet machining device, the structure is simple, machining efficiency is high, and the problem of low-temperature quick machining of a hydrophobic polymer is solved.