The invention discloses a manufacturing method of an S-shaped beam. The manufacturing method comprises the steps of (1), plate adjustment; (2) OP10, drawing; (3) OP20, front trimming and front punching; (4) OP30, upper flanging and side shaping; (5) OP40, side trimming and side punching; (6) OP50, side flanging, side punching and punching; (7) OP60, punching and side punching. According to the manufacturing method, on the premise that the quality and precision of the punched part are guaranteed, the number of procedures can be decreased, the production efficiency can be improved, and the production cost can be lowered. After staggered laser butt welding is performed on plates in an unequal-thickness mode, the strength of a body-in-white is guaranteed, the weight of the body-in-white is reduced, and energy conservation and emission reduction are effectively achieved.