The invention discloses a vacuum cracking apparatus for a power battery and a cracking method thereof. The cracking device includes a cylinder and further includes a rolling device, a first sealing device, a cracking device, a second sealing device, a pyrolysis device and a third sealing device which are arranged from top to bottom. The cracking device for the power battery of the present invention is equipped with the first sealing device, the second sealing device and the third sealing device to isolate the cracking device from the pyrolysis device and be capable of realizing material transmission and gas isolation without interference with each other, so that gas stirring between an anaerobic zone and an aerobic zone is avoided; and by combing battery cracking and battery pyrolysis, with cracked gas discharged after cracking as a fuel for cracking and pyrolysis or preheating a pyrolysis device, resources are fully used.