The utility model provides a combined type liquid state forging mould for a complex aluminum piston, which belongs to a mould. The utility model is provided with a bottom die which is installed on a lower die holder, and the lower die holder is installed on a lower shim plate. A concave die center washer is arranged on the lower die holder, the inside of the concave die central washer is provided with a combined concave die, and the external side of the concave die center washer is provided with a concave die housing washer which is fixed together with the lower shim plate. A push rod is arranged under the bottom die, an upper pressure head corresponding to the push rod is arranged on the combined concave die, and the upper part of the upper pressure head is fixed on an upper shim plate through a fixing washer. Pin cores which are arranged on the combined concave die, the concave die central washer and the concave die housing washer are connected together with piston rods on pin core oil cylinders through joints. The liquid state forging mould realizes the one-time molding of the liquid state forging of the complex aluminum piston, and finishes the history that an export seat and the outer deviation of the liquid state forging aluminum piston have to depend on mechanical processing; the utility model has the advantages of high work efficiency and low processing cost of the aluminum piston.