Cylinder head is a box part with complex structure. It is machined with inlet and exhaust valve seat holes, valve guide holes, spark plug mounting holes (gasoline engines) or fuel injector mounting holes. A water jacket, an air inlet and exhaust passage and a combustion chamber or a part of the combustion chamber are also cast in the cylinder head. If the camshaft is installed on the cylinder head, the cylinder head is also machined with cam bearing hole or cam bearing seat and its lubricating oil passage.

The cylinder head of water-cooled engine has three structural forms: integral type, block type and single type. In a multi cylinder engine, if all cylinders share a cylinder head, the cylinder head is called an integral cylinder head; If there is one head for every two cylinders or one head for every three cylinders, the cylinder head is a block cylinder head; If each cylinder has a head, it is a single cylinder head. Air cooled engines are all single cylinder heads.