本文主要论述阶比谱分析方法及其在汽车起动电机故障实时诊断中的应用。首先阐述了阶比谱分析的原理以及阶比采样中混迭与泄漏的产生及其抑制方法，然后讨论了如何在起动电机运行过程短、升速快的情况下获取感兴趣的噪声信号，进而采用阶比谱分析方法从信号中提取故障特征信息，最后利用阀值判别法起动电机的故障进行实时诊断。 This article mainly discusses the method of order spectrum analysis and its application in the real-time fault diagnosis of automotive starting motor. Firstly, the principle of order spectrum analysis and the generation and suppression of aliasing and leakage in order-ratio sampling are described. Then, how to obtain the noise signal of interest when the starting motor runs short and the speedup is fast is discussed. Using order spectrum analysis method to extract the fault characteristic information from the signal, and finally using the threshold to judge the fault of the motor for real-time diagnosis.