The invention relates to a back bar fastener used for fixing a back bar and a using method for the back bar fastener. The back bar fastener comprises a fixing piece and a sliding piece, wherein the fixing piece and the sliding piece are arranged in a intersecting mode and are movably connected; one end of the fixing piece is a connecting end, the sliding piece slides along the fixing piece to clamp and fasten the back bar. The back bar fastener is simple in structure, easy to operate and beneficial to quick disassembling. The using method for the back bar fastener comprises the following steps that the back bar fastener is arranged; the back bar fastener is fixedly connected with a aluminum alloy template by utilizing the connecting end; the back bar is placed on the back bar fastener, so that the sliding piece slides to a proper position; the back bar is placed between the aluminum alloy template, the upper side face of the fixing piece and the left side face of the sliding piece; the back bar is clamped tightly; the sliding piece is knocked to clamp the back bar tightly. The using method for the back bar fastener is easy to operate and beneficial to quick disassembling.