A multi-chip stack package structure comprises a substrate, which has a chip placement area defined on its upper surface and a plurality of contacts disposed outside the chip placement area; a first chip is disposed in the chip placement area with the rear surface, a plurality of first pads being disposed on the active surface and a plurality of first bumps each being formed on one of the first pads; a plurality of metal wires connect the first bumps to the contacts; a second chip with a plurality of second pads being disposed on the active surface and a plurality of second bumps each being formed on one of the second pads, the second chip being mounted to the first chip with its active surface facing the active surface of the first chip, wherein the second bumps correspondingly connect the metal wires and the first bumps respectively.