Abstract: There are considerable numbers of non-electrified lines both domestically and internationally, and energy conservation and environmental protection have also put forward higher requirements for the design and operation of rail transit vehicles. The new energy-saving and environmentally friendly hybrid electric multiple units could effectively solve the current contradiction and is a necessary path in the process of social development. However, the research on hybrid electric multiple units by domestic rail transit host companies is still in its early stages of development, and there is currently no mature design and application performance. Therefore, this article focuses on analyzing and introducing the overall system architecture and key technical routes in the development and design process of hybrid electric multiple units, such as vehicle flow control, internal combustion power package technology, traction system main circuit, vehicle weight control and equipment layout, cost, etc. This article has important guiding significance for the design of hybrid power source rail transit vehicles in the future.