A display module substrate and a manufacturing method thereof are provided. The display module substrate includes a substrate body and a plurality of signal circuits. The substrate body has a supporting surface. The supporting surface includes a viewing area and a signal circuit area on one side of the viewing area. The signal circuits are disposed on the supporting surface and located at the signal circuit area. The signal circuit area has a plurality of apertures running through the substrate body, wherein the apertures are not shielded by the signal circuits. In a manufacturing thereof, the substrate body is disposed on a transparent carrier plate. When high-energy light is applied through the transparent carrier plate to etch a bottom surface of the substrate body to separate the substrate body and the transparent carrier plate, the resulting gas leaves through the apertures.