Abstract: For a non-road diesel engine, the zero-dimensional calculation of its cooling system was carried out in the forward development process.The in-cylinder heat transfer, EGR heat transfer, friction heat transfer and other data were obtained through GT-POWER performance calculation, and the total heat needed to be removed by the cooling system was estimated.Subsequently, the coolant demand of the engine cooling system was estimated according to the set temperature difference of water jacket and EGR cooling as well as flow rate of other cooling components, so as to guide the water pump selection and provide the boundary conditions for the subsequent 1 D and CFD（computational fluid dynamics） calculation of the cooling system.