The cylinder head is generally made of high quality gray cast iron or alloy cast iron, and the gasoline engine used in the car is mostly made of aluminum alloy cylinder head. Aluminum alloy has good thermal conductivity and is beneficial to improve the compression ratio of engine. Secondly, the casting performance is excellent, suitable for casting parts with complex structure. But attention must be paid to the cooling of aluminum alloy cylinder head, to control the temperature of its bottom plane at 300℃ below. Otherwise, the bottom plane overheating will produce plastic deformation and warping.