The performance of the hybrid power source at low temperature is experimentally analyzed. The parallel connected electric double layer capacitor (EDLC) enhances the power of Li-ion battery as it acts as a buffer in charge and discharge processes, especially at low ambient temperature. The behaviors of current and voltage of both the battery and EDLC are studied by experiments and described by a mathematical model. The EDLC can share a great part of total current load at low temperature, which effectively release the battery stress in pulse charge/discharge processes. Moreover, adding an EDLC in parallel with the battery also exhibits a considerable increase in capacity as compared to the Li-ion battery standalone in pulsed and continuous discharge processes. The performance of the hybrid power source under practical drive cycle is also studied in this article.