A backlight module and a method for manufacturing a base thereof are provided. The backlight module base includes a back plate and a frame. The back plate has a plate body and at least one sidewall, which includes a wall body and a folding structure bending from the top of the wall body. The folding structure, the plate body, and the wall body together enclose a groove. The frame is formed on the plate body and adjacent to an inner surface of the sidewall. A part of the frame is embedded into the groove. The engagement between the frame and the groove increases the contact area between the frame and the back plate to improve the connection strength. In addition, the folding design of the sidewall increases the rigidity of the whole structure.