The design of propulsion system for CNG-electric hybrid city-bus is introduced based on the selection of driving cycle and the establishment of control strategy. Making program of powertrain’s configuration is included as well as parameters’ selection and matching of components such as engine, motor, battery and transmission. The simulation results show that the design meets the requirements. The components of the propulsion system are integrated together, and then they are installed into the sample city-bus. The roadway test has been done under the target driving cycle. Compared with the peer CNG city-bus, there are 28% increasing in the largest climb degree and the acceleration time of 0~50 km is reduced more than 1.8 s, and the fuel saving rate achieves to 22% under the typical city-bus driving cycle of China.