The invention belongs to the field of continuous casting and rolling of steel, in particular to a production method for controlling the straight crack defect of a surface edge of a medium-thick plate. The production method comprises the steps of steelmaking, chamfer blank continuous casting, chamfer blank angle part on-line cleaning, a casting blank entering a heating furnace for temperature rising and soaking, rough rolling, fine rolling, and finishing storing. A chamfer blank is provided with eight original chamfers, wherein in the step of chamfer blank continuous casting, the chamfer blank is produced through a chamfer crystallizer. After the chamfer blank goes out of a casting machine and before the chamfer blank goes into the heating furnace, on-line angle cleaning is conducted on angle parts of adjacent wide faces of the chamfer blank. After the on-line angle cleaning is conducted on the chamfer blank, thin and small occluded foreign substances, air holes and micro-segregation defects existing in the angle part of the casting blank can be eliminated, and the corner angle shape of the angle part, of the casting blank, of the adjacent wide faces can be changed, so that the high-temperature ductility of the angle part of the casting blank in the rolling process is improved, and tensile stress centralization in a transverse rolling process is reduced. Consequently, the production method can effectively control the occurrence of the straight crack defect of the edge of the medium-thick plate.