The invention discloses a combined cylinder body manufacturing method for an aluminum-alloy liquefied petroleum gas cylinder. The method comprises the steps of blank heating, cylinder body extruding and cylinder body welding. The method particularly comprises the steps that an aluminum-alloy round-rod ingot blank is cut into cylinder body blanks, and then the cylinder body blanks are put into a heating furnace for heating; and the heated cylinder body blanks are put into a mold cavity of an extruding machine to be extruded and formed into finished cylinder body products, and the finished cylinder body products subjected to extruding forming are spliced and welded into a whole, wherein the height of the mold cavity is h, and h is a positive number and larger than the height of a pressure head. According to the combined cylinder body manufacturing method for the aluminum-alloy liquefied petroleum gas cylinder, metal can flow uniformly in the extruding process; compared with parts manufactured through a traditional punching method, the size precision is high, cylinder bodies with thinner thicknesses can be manufactured, the interior tissue of the cylinder bodies is more compact, the self weight of each cylinder body is greatly reduced, the tolerance pressure is higher than that of a traditional liquefied petroleum gas cylinder, the cylinder body performance is better compared witha traditional punching manner, and the safety is further improved. Compared with the prior art, the manufacturing procedures of the gas cylinders are reduced, the production and processing efficiencyis improved, and the production cost is reduced.