"The fundamental way out for agriculture is being mechanized". Engines are widely used in modern agricultural machinery, and they occupy an important position. This course gives a detailed introduction to the structure of modern agricultural engines. The organization and implementation of the main contents include the overall understanding of agricultural engines, the structure of the crank and connecting rod mechanism, the valve mechanism, the fuel supply system of the diesel engine, the cooling system, the lubrication system, starting system, the ignition system of the gasoline engine, diesel engine use and maintenance, etc.