An engine piston mainly comprises the top of the piston, the head of the piston, the skirt section of the piston and the pin boss of the piston, and is characterized in that: the head of the piston is of a flat topping calathiform shape, an evading valve pit is arranged on an adaptation valve. At least one beveling arch groove (nick) is arranged on the edge of the calathiform near the inlet side oil atomizer. Because the head of the piston of the invention mainly adopts the flat topping calathiform shape and at least one beveling arch groove (nick) is arranged at the side of the oil atomizer near the inlet side on the edge of the calathiform, fuel and the air can be mixed fully, a state of a spark plug being the center and stratified gas mixture being from density to diluent is formed, the gas mixture gathered around the spark plug is very thick, so the ignition is very easy and stratified combustion is realized. The invention is especially suitable for DGI engine.