Engine piston capable of automatically changing compression ratio

The invention discloses an engine piston capable of automatically changing the compression ratio. The engine piston is characterized in that the engine piston comprises a piston head and a piston skirt, the piston head is movably connected with the piston skirt through a limiting washer, relative displacement between the piston head and the piston skirt is limited through the limiting washer, and compression springs are arranged between the piston head and the piston skirt. According to the damping type compression ratio-changeable piston, the compression ratio can be automatically changed, the thermal efficiency of partial loads of a gasoline engine can be improved, knocking in the full-load process can be avoided, and reliability and economical efficiency of an engine can be effectively improved. By means of simulation computation, for passenger-vehicle fuel consumption test cycle (NEDC), fuel consumption is reduced by 5%-7% compared with an engine with a fixed compression ratio, and the production cost is