SEAT Department of SAIC Motor Vehicle Company starts innovatively applying the single motor and P2.5 configuration scheme from EDU G2(Electric Drive Unit Generation 2), which consists of six engine gears and four motor gears. EDU G2 is very compact and adaptable through the coupling design. Gear coupling make the engine and motor coordination limited, so as to the high efficiency zone of the engine and the high efficiency zone of the motor cannot match in some working conditions, which affect the performance of the vehicle. Therefore, SEAT developed the second generation of single-motor plug-in hybrid system EDU G2 Plus EDU G2(Electric Drive Unit Generation 2 Plus), which realized the decoupling design of 5 engine gears and 2 motor gears, so that the power output of engine and motor is freely. With excellent power and economic performance, the vehicle has been well received by customers. The article mainly describes the system design and development on the themes of motor performance improvement, system efficiency improvement and NVH optimization. SEAT takes the lead in adopting the hair-pin motor winding scheme, compared with the ordinary circular motor, the slot full rate of the Hairpin motor is increased by 20%~25%. The number of motor windings is increased from 2 layers to 5 layers, the maximum efficiency and comprehensive efficiency of the motor are significantly improved. Compared with the EDU G2, EDU G2 Plus has been optimized in some mechanical paths, including application of low roll resistance bearings, matching and selection of lubricating oil, optimization of cooling and lubrication system. In NVH performance , through motor body optimization and gear modification, the motor gear is reduced from 41 to 27 order, providing a more comfortable experience for the vehicle. The innovative scheme design of this paper provides a reference for the design and mass production of hybrid P2.5 configuration Plug-in Hybrid System.