Abstract: In recent years, effects of agricultural vehicles, especially tractors on the environment and resources are increasing year by year, so carrying out the research and development of energy-conservation and environmental protection tractors, especially hybrid electric tractors has become the imminent important subject. And the power coupling is the core of hybrid electric drive system. According to the requirements of working properties and transmission characteristics of tractors, the transmission ratio, characteristic parameters and matching number of gear teeth of power coupling device for hybrid electric tractor were designed. Based on the requirement of transmission load and manufacturing technology, the structure design and strength check were processed. Then a new power coupling for parallel hybrid electric tractor was developed, which was also tested on self-developed hybrid electric tractor test-bed. The results showed that the power coupling device can meet the needs of working characteristic under working condition. In addition, the output speeds were sensitive with the speed changes of power sources, and had excellent ability in real-time speed changing while the output torque was insensitive with the speed changes of power sources. The development of power coupling device provides the foundation for further research on hybrid electric tractors.