Aimed at the drawbacks of traditional tractors, such as complicated transmissions, inefficient transmission systems, heavy fuel consumption rates, and high exhaust gas emissions, the design method of the tractor’s series hybrid electric drive systems was put forward by calculating its plough operation rated traction. A feasible formation was given and included design methods of the electric tractive motor, weight parameters, and prime energy systems, which consist of a diesel engine and a generator of the powerful tractor’s hybrid electric drive systems. Transmission ratios of the series hybrid electric tractor drive systems were designed to follow with differences of working load rates under commonly used working conditions, while making sure of the efficiency and capacity of transmission systems. Its storage battery parameters were designed to fill the traction power requirement, which is from the changing load situation when the tractor worked under a light gear. The YTO-1804 wheeled tractor has been taken as the investigative object, its series hybrid electric drive systems have been designed by using the aforementioned method. Upon analysis of its tractive characteristics, the results conveyed that the installed tractor’s working adaptability and tractive characteristics are better when it compared with the original tractor. Output of the electric motor is suitable with the requirements of a heavy load working circumstance. The curve portrayed that the relation between the traction force and the traction power of the installed tractor could cover the original tractor’s working area. The installed tractor’s transmission is more efficient and its structure is simpler. Combined with the relevant slippage test results to analyze the installed tractor’s slippage situation, changes in slippage rate followed with changes in driving force are acceptable. Based on the analysis of the difference of equivalent fuel consumption rates between the two types of drive systems, the analysis of the relevant curve, the relevant status of the installed tractor were on the bottom of original tractor’s curve. The result proved that the installed tractor has a better fuel economy. Continuously variable function can be reached under a definitional gear. When the tractor is on the working model or the driving model, the most important performance parameter has a wide regulation range. Based on plough operation, furrow plow number and the product of tilling depth value with specific resistance value was seen as an index of the tractor’s working load, the result proved that the original tractor’s common working area can be distinguished with the relevant gears setting intention, and it has higher efficiency when the load rate is higher. As well, the traction efficiency can be improved 2.98%on average. So, different working requirements of investigative objects can be reached well. The design method laid the foundation for the following study of the powerful tractor’s series hybrid electric tractor drive systems.%针对传统拖拉机存在变速器结构复杂、传动效率低、高油耗、高排放等问题，提出一种基于犁耕工况下串联式混合动力拖拉机驱动系设计方法，包括确定传动方案、匹配牵引电动机和主能源功率参数及设计变速器挡位和辅助能源参数等。基于提出的设计方法，以东方红1804拖拉机为研究对象，对其串联混合动力驱动系主要参数进行了设计计算，分析了其牵引性能，结果表明：混合动力拖拉机特性曲线在有效牵引力范围内完全覆盖原拖拉机的工作特性场，且牵引效率较高；发动机同机械传动装置解耦，等效燃油消耗率平均降低了2.64%；变速器结构得到较大简化，传动效率较高；变速器速比设置合理，可满足拖拉机不同作业工况下对负载的需求，同时实现了无级变速。该研究为混合动力拖拉机能量管理策略、换挡规律及控制系统的设计提供了理论依据。
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