The invention provides a one-mold multi-pass formed metal plate machining method which is used for machining skin parts, provided with the step structure, in aeronautical parts. The method comprises the steps that a, a plate is put on two lower mold sets; b, the relative positions of a plurality of upper mold blocks of an upper mold set till the multiple mold blocks of the upper mold set make contact with the plate; c, the upper mold set moves downwards, and the position, between the two lower mold sets, of the plate is bent and deformed; d, the plate is moved by the feeding distance, the stepb and the step c are repeated till bending and deformation, in the feeding direction, of the plate meet the final shape requirement; and e, the plate is taken out, and forming is completed.