Disclosed is a backlight module backplane, which includes a frame and a board. The frame includes a first sidewall, a top wall, a second sidewall, and a bottom wall that are sequentially connected in an end-to-end manner. The first sidewall and the second sidewall are of a straight plate structure. The top wall and the bottom wall are of a curved plate structure. The board has four edges respectively positioned against and fixed to the first sidewall, the top wall, the second sidewall and the bottom wall, so that the frame sets the board in a form of a curved surface. The backlight module backplane has reliable accuracy of curvature, a reduced weight, and a low cost. Also disclosed are a backlight module and a liquid crystal display device.