A frozen forming method for a large-size thin-walled aluminum alloy component using an aluminum alloy tailor-welded plate is described. An aluminum alloy tailor-welded plate is cooled to a temperature with a cryogenic fluid medium, and temperature of a weld zone is regulated to be lower than that of a base metal zone; and the component is fabricated by a tool integrally with aluminum alloy tailor-welded plate, by placing aluminum alloy tailor-welded plate onto tool; assembling tool and filling with cryogenic fluid medium so temperature of tool is −150 to −196 degrees Celsius; and apply pressure to deform the aluminum alloy tailor-welded plate when temperature of a weld zone reaches −150 degrees Celsius to −196 degrees Celsius, thereby facilitating forming the aluminum alloy tailor-welded plate to a designed shape of the aluminum alloy component; and disassembling the tool, and taking out the aluminum alloy component.