Abstract: In order to meet the diversity of tractor product configuration, further increase the tractor traction power, improve the tractor operation through the requirements; assembly of four-wheel drive transfer case assembly is an indispensable important configuration module.Taking wheeled tractor as an example, the design method of modular four-wheel drive transfer case assembly for mechanical shift gearbox tractor and power shift gearbox tractor was listed.This paper introduces the design process, design principles, and matters needing attention of the four-wheel drive transfer case assembly.This method provides a complete set of design steps, requirements, difficulties and key points, and provides a solution for the subsequent development and design of four-wheel drive transfer case assembly.