According to the theory of hybrid electric drive train and requirements of working properties and transmission characteristics of tractors, a drive train for parallel hybrid electric tractor (PHET) was designed. Evaluation indicator and calculation model for dynamic and economic performance of hybrid electric tractor (HET) were suggested based on the theory analysis of traction characteristics of HET. The parameter design methods of each component of drive train were discussed. The theory of design and calculation method for drive train of HET was proposed. Taking a designed HET as study object, the changing relationship of driving force and climbing property with the speed changing of engine and motor under different gearshift when engine was working on 60% and 40% of load, and the changing relationship of equivalent energy consumption for 1h steady operation on plowing with the speed changing of engine and motor under different gearshift were analyzed by calculating. The calculation result of plowing status was checked by simulation model. Results showed that driving force and climbing property were directly proportional with the load of engine, but speed matching range of engine and motor decreased with the increasing of working load of engine. Moreover, when plowing, the error rate was not over 4% in maximum between calculation result and simulation result, and when increasing the speed of engine and motor, equivalent energy consumption increased under a certain gearshift. Furthermore, the energy conservation of HET was higher by 24% in maximum compared to traditional tractor with the same power. 