A fabrication method of a package structure includes: preparing a metal plate having first and second surfaces and defined with an active region; forming a wiring layer with conductive traces and first electrical contact pads on the first surface; forming third electrical contact pads corresponding to the first electrical contact pads on the second surface; forming a first encapsulant on the first surface; forming on the second surface an open area to penetrate the metal plate, wherein the metal plate form conductive posts between the first and third electrical contact pads; mounting in the open area a chip electrically connected to the wiring layer; forming a second encapsulant in the open area, the wiring layer and the third electrical contact pads; forming first and second openings in the first and second encapsulants to expose the third electrical contact pads, respectively; and cutting the metal plate to remove the metal layer.