The present disclosure provides a back plate splicing structure for large-size backlight modules. The back plate includes a bottom flat plate and a splicing member joined to an end of the bottom flat plate, wherein the splicing member includes a side plate, and an upper supporting plate and a lower supporting plate configured on a same side of the side plate; the upper supporting plate, the lower supporting plate, and the side plate cooperatively define a clamping opening clamping the bottom flat plate therein; the upper supporting plate fixes the bottom flat plate in the clamping opening, and at least one fixing screw is configured between the bottom flat plate and the splicing member.