The invention relates to an electric control unit test system and belongs to the electronic test field. The electric control unit test system comprises a signal conditioning and control device in connection with an electric control unit through test cables and an industrial control computer in connection with the signal conditioning and control device through a serial port, wherein the signal conditioning and control device comprises a current sensor, a drive circuit, a relay module, a sampling circuit, a communication module, a central processing unit (CPU) and a power supply module. The power supply module is in connection with other components through power lines, the communication module is in connection with the industrial control computer through a serial port and is in connection with the CPU through data lines, the sampling circuit is in connection with the electric control unit through test cables, the CPU and the drive circuit, the drive circuit and the replay module, the replay module and the sampling circuit, and the sampling circuit and the CPU are all in connection through data lines, and the current sensor and the power supply module are also in connection through data lines. The electric control unit test system is of a modular design and has the advantages of being convenient to maintain, accurate in fault positioning, reliable in testing and convenient to test.