The utility model discloses an engine piston cooling structure. The engine piston cooling structure comprises a piston, the piston is connected with one end of a connecting rod through a piston pin, and the other end of the connecting rod is connected with a crankshaft. An inner cooling oil duct is formed in the piston, a connecting rod oil duct which penetrates through the two ends of the connecting rod is formed in the connecting rod in the axial direction, and an axial oil duct is formed in the crankshaft. An oil injection opening which is communicated with the axial oil duct is formed in the radial direction in the position, corresponding to the cross section part of the connecting rod oil duct, of a connecting rod neck in which the crankshaft and the connecting rod are connected. The piston pin is provided with a main oil duct along the axis, and sealing plugs are arranged at the two ends of the main oil duct. Annular oil grooves are formed in the positions respectively, namely in the middle corresponding to the connecting rod oil duct, and at the left and right ends of the circumferential face of the piston pin, and the three annular oil grooves in the piston pin are further provided with radial oil ducts which are communicated with the main oil duct in the radial direction. Oil inlets are formed in the positions, corresponding to the annular oil grooves in the left end and the right end of the piston pin, of the inner cooling oil duct respectively, and oil outlets of the inner cooling oil duct are communicated with an inner cavity of the piston. The engine piston cooling structure is simple in overall structure, high in reliability and capable of improving the cooling efficiency of engine oil.