The powertrain of an ultra-capacitor-based parallel hybrid electric vehicle (HEV) was developed. Innovations, such as the engine management system, floating ISG (Integrated Starter and Generator), electronic-controlled double-clutch system and dual-driven air conditioning system were realized. Hybrid control strategies to improve the fuel economy and reduce emissions were analyzed briefly. In order to ensure the vehicle emission performance, the engine management system calibration was performed. The vehicle emission test was also conducted, showing that the vehicle emission satisfied the EURO III standard and has great potential for improvement. The hybrid start test was introduced in detail. We realized the hybrid function and start parameter optimization of the engine and ISG.