Energy storage and power boost are major problems in the development of electric vehicles (EV). Installing a super-capacitor as an auxiliary power source to improve the performance of electric vehicles is a feasible and realistic solution. In this paper, the structure of a multi-energy system and the principles of flow of the multi energy of electric vehicles were introduced first, explaining how different sources of energy work in different situations. A model of electric vehicle with a battery and a super-capacitor, based on Matlab/Simulink was built up. The model was validated by comparing the simulation results and the actual data from later field tests. The drive cycle used in the simulation was the CYC_CONST_45. Comparisons were made between the model of the vehicle with a super-capacitor and the model of a vehicle without a super-capacitor. Field tests of an electric vehicle were conduct and analyses were made. The analysis includes vehicle dynamic performance and economical performance in urban environments where the vehicle accelerated and decelerated frequently. The results showed that installing a super-capacitor improves the working conditions of the battery. The variation of the current drawn by the vehicle was smoothed due to the working of the super-capacitor, which provided better working conditions for the battery and increased the operating life of the battery. A super-capacitor can also improve the acceleration performance of the vehicle. The super-capacitor could provide large current in short time, delivering extra energy to meet the energy requirement when it is needed. A battery and a super-capacitor working together can reduce the average energy consumption. The average energy consumption of a vehicle with a super-capacitor is only 77% of that of a vehicle without a super-capacitor. The mileage in one charge of the electric vehicle will enlarged notably