The piston of the automobile engine is one of the main fittings in the engine, which forms the piston group with the piston ring, piston pin and other parts, and the cylinder head and so on together form the combustion chamber, bears the gas force and transmits the power to the crankshaft through the piston pin and connecting rod, in order to complete the working process of the internal combustion engine. Because the piston is in a harsh working environment at high speed, high pressure and high temperature, and to take into account the smooth and durable operation of the engine, it is required that the piston must also have sufficient strength and stiffness, good thermal conductivity, high heat resistance, small expansion coefficient (small size and shape changes), low relative density (light weight), wear and corrosion resistance, And the cost is low. Because the requirements are many and high, and some of the requirements contradict each other, it is difficult to find a piston material that can fully meet the requirements. Modern engine piston is generally made of aluminum alloy, because aluminum alloy has a small density, good thermal conductivity of the outstanding advantages, but at the same time has a relatively large expansion coefficient, high temperature strength is poor disadvantage, these shortcomings can only be through a reasonable structural design to meet the requirements of use. Therefore, the quality of the car engine, not only to see the use of materials, but also to see the rationality of the design.