The battery of the automobile generator test system adopts the ordinary vehicle battery. It needs to be fully charged before the test to provide excitation power for the vehicle generator. Speed ​​sensor uses LJ12A4-4-Z/BY's inductive proximity switch as a sensor, which is a non-contact detection device that can convert the generator speed into a voltage signal output and pass the data acquisition card to the main control unit. The multi-function data acquisition card adopts PCI-6034E type. This type of data acquisition card is a multi-function data acquisition control card based on 32-bit PCI bus. It supports DMA mode and buffer mode. It supports single-pole and bipolar analog signal input. The rate is 16bits, the sampling frequency is 200kS/s, the signal input range is ±10V, 16 single-ended/8-channel differential analog input channels, TTL digital I/O ports, and 2 24-bit timer counters. In order to measure the no-load characteristics, output characteristics and external characteristics of automotive generators, virtual instrument software LabVIEW interface was designed according to actual needs. After the hardware is connected, measurement is started. First, the no-load measurement is performed, ie, the generator is idling, the output current is 0, and the relationship between the voltage and the rotation speed of the output terminal of the generator is measured. Then measure the output characteristics, that is, the generator terminal voltage is maintained at 14V. Measure the relationship between the generator output current and the generator speed to determine the generator's no-load speed and full-load speed. Finally, the external characteristics of the generator are measured, that is, the generator maintains a certain rotation speed, and the relationship between the generator terminal voltage and the output current is measured. In actual measurement, the generator speed is adjusted to 2000r/min. Through the measurement of the above three characteristic curves, the performance of the tested automobile generator can be judged.