The invention provides a forming process of a 5M-grade storage tank spherical melon petal. The forming process comprises two times of drawing formation; the quenching treatment is performed in middle; the artificial aging treatment is performed after final drawing; and the forming process produces a part satisfying the design requirement through adjusting process parameters. The forming process specifically comprises such steps as blanking, pre-drawing formation, quenching, final drawing formation, allowance removal and artificial aging. The forming process has the following beneficial effects: the deformation quantity of pre-drawing and final drawing in the drawing formation procedure is reasonably controlled according to the material thickness of an original blank of 2219 melon petal; and the surface quality of the part totally satisfies the product design requirement through controlling the drawing formation process.