An OLED display device and a fabrication method thereof are provided. The OLED display device, includes: an array substrate and a package substrate cell-assembled, wherein, the array substrate includes a first base substrate, an anode layer, a cathode layer and an electroluminescent layer disposed between the anode layer and the cathode layer, the anode layer or the cathode layer is disposed as an upper most layer of the array substrate; the package substrate includes a second base substrate and a graphene layer, the graphene layer is disposed as an upper most layer of the package substrate; a conductive filler is provided between the array substrate and package substrate, the graphene layer is electrically connected with the anode layer or the cathode layer disposed as the upper most layer of the array substrate via the conductive filler.