For verifying the strategy of the Vehicle Control Unit(VCU), a real-time simulation environment needs to be established in advance. It is modified from our in-house simulator for the Electric Vehicle (EV) based on the Hardware in-the-Loop(HIL) structure and constrained by several communication devices, e.g. CAN bus, AI/O, DI/O, etc.. A Dual Energy Storage System (DESS) has been modeled in this simulator. It is composed by a Li-ion battery set and an ultracapacitor in the form of equivalent circuits based on empirical results. Specific driving patterns are utilized as an input to this visual EV simulator. The outputs are the battery SOC, ultracapacitor voltage, energy consumption and the driving mileage. By comparing these outputs of DESS under the giving driving pattern, it could also help determine the combination ratio of the DESS.