Preparation method of low hydrogen brittleness level narrow copper bar

The invention discloses a preparation method of a narrow copper bar with a low hydrogen embrittlement grade. The technological process of the preparation method comprises the steps of smelting, up casting, cold deformation, annealing, four-roller flattening, annealing, drawing and rolling packaging. Through rolling forming after cold machining and heat treatment of an up-drawing casting blank, the inherent defects of an existing continuous extrusion technology are avoided, the layering defect is eradicated, meanwhile, pressing and broadening in the flattening process are controlled, annealing treatment is combined, edge cracking of the copper bar under large width-thickness ratio deformation is avoided, the uniformity of a grain structure is guaranteed, and the yield of the copper bar is improved. The requirement for friction stir welding is met, the narrow row with the width-to-thickness ratio ranging from 5 to 15 is prepared, and the requirement for high reliability of a new energy battery is met through th