Abstract: Based on the research on inertia air-charging of 195 single-cylinder diesel engine used in agriculture in 80's by author, the thesis analyzed the transience of air-charging system of double-cylinder diesel engine during working. The defects in original design that leads to loss of efficiency in air-charging were pointed out, and a new design criterion of air-charging system data based on the principle of inertia air charging was put forward. In the contrast test, an extra power was obtained by 13% under specified rotational speed.