The invention provides a plate-free tray type offshore substation upper module which comprises two layers of frame type steel structures, each frame type steel structure is formed by beams, columns and inclined struts, and main columns, structural columns and inclined struts are arranged between the upper layer of beams and the lower layer of beams; a prefabricated cabin or outdoor equipment is connected to a beam or a column of the frame-type steel structure to form an integral offshore transformer substation upper module. According to the frame type steel structure, a beam system serves as a framework of the plate-free tray structure type, grating channel areas are only arranged on a channel area, an equipment overhaul area and an embarkation gathering area on two layers of trays of an upper module of the plate-free tray structure type offshore transformer substation, and ribs and steel bed boards are not arranged on all the areas. A two-layer steel structure arrangement mode is adopted, original third-layer and fourth-layer beams, columns, ribs, plates and the like are omitted, meanwhile, first-layer and second-layer ribs, steel bed boards and the like are omitted, the using amount of steel can be reduced by about 50%-60%, the weight of an upper module is reduced, and then the choices of construction ship machine equipment are increased.