The utility model provides a welding forged steel integral piston, which belongs to an engine piston. The engine piston is provided with a forged head and a forged skirt which are welded and fixed into a piston body. Between a ring groove and a burning chamber, the piston body is provided with a cooling oil chamber communicated with the inner cavity of the piston body through an oil inlet/outlet. The skirt below the ring groove is provided with an annular groove. Compared with an integrally forged piston, the piston has better manufacturability, particularly simplified processes for forging piston blanks and forming the cooling oil cavity, simpler fabrication and smaller residual stress of the blank. Due to the closing cooling oil cavity formed by welding, the integral structure rigidity of the piston is increased. The annular groove above the piston skirt is communicated with the inner cavity of the piston in the long axis direction, which lightens the weight of the piston body, helps engine oil return to the position of the oil ring groove, simultaneously increases the flexibility of the skirt and helps to reduce cylinder matching gaps and lower engine oil consumption.