Hardware-in-the-Loop simulation technology, with its advantages of high safety, strong condition reproduction capability, and high testing efficiency, has become an indispensable core verification method in the development process of electric drive systems. In response to the high cost of traditional test benches and the difficulty in simulating extreme conditions, this paper has constructed an HIL test system for electric drive systems, enabling separate HIL testing of MCUs and TCUs, as well as combined HIL testing. Through typical conditions, transient dynamic responses, and extreme fault injection tests, the real-time performance, reliability, and stability of this HIL test system have been verified.