Abstract: State Ⅲ diesel engine began to be implemented in agricultural machinery.Environment can be protected effectively by low emission .And the ECU can display important parameters of diesel engine in real time by CAN bus.Once there is a fault，alarm and feedback was diaplaied on screen immediately，which is more intuitive and accurate.For superiority of state Ⅲ diesel engines，it was applied to silage harvester successfully.It will promote and facilitate state Ⅳ，Ⅴ diesel engine in promotion and popularization of agricultural machinery.