As an effective approach for the design, implementation and test of control systems, hardware-in-the-loop (HIL) test has been used in many research areas. This paper describes a real-time HIL simulation test for an automotive electronic control system. The HIL system proposed in this paper consists of three parts: real-time target hardware, electronic control unit (ECU) of the automotive electronic control systems and a signal-conditioning unit which regulates the voltage levels between real-time target and ECU. The HIL simulation evaluates mechanical and electronic behaviors in real time using off-line simulation models by interfacing real-target with electrical control units via interface box. The model has been developed by MATLAB/Simulink. The model is composed of mechanical part which predicts dynamic behaviors and electronic part to calculate the motor speeds, current and electronic loads under the various conditions. By considering those dynamics, precise current behaviors like surge current can be evaluated in real-time. Interface box for conditioning voltage level and evaluate load and current has several channels, and it enables HIL test with several ECUs together. From this, user can investigate interaction of target ECU with others. The off-line simulation models and HIL system have been validated by comparison the results, which are current, motor speed and hall sensor feedback signals, with measurements on real electronic control systems.