MEMS microphone packages and fabrication methods thereof are disclosed. A MEMS microphone package includes a casing with a conductive part disposed over a substrate, to enclose a cavity. A MEMS acoustic sensing element and an IC chip are disposed inside the cavity. An opening with an acoustic passage connects the cavity to an ambient space. A first ground pad is disposed on a backside of the substrate connecting to the conductive part of the casing through a via hole of the substrate. A second ground pad is disposed on the backside of the substrate connecting to the MEMS acoustic sensing element or the IC chip through an interconnection of the substrate, wherein the first ground pad and the second ground pad are isolated from each other.