In this paper, we did not manufactured actual prototype of DC-DC converter for supplying power to the electric system and charging electric battery of the electric bus, but implemented modeling of input power, product power and electric battery such as switching devices, diode, transformer, chock, capacitor, etc. using MATLAB Simulink, in order to carry out test by interoperation with a virtual environment equipment, HILS (Hardware In the Loop Simulation) at control board level. After we have fabricated first control board only out of designed elements on the prototype, implemented interface environments to allow it to be interoperated with HILS system from dSPACE Inc. and checked if the modeled input/output and power devices are matched with the actual elements, we have mounted the same operation program as the actual control on the control board. We have confirmed its operation performance through waveform and finally formed failure mode to check if the product normally carries out protection mode.