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In order to obtain the variation law of the acoustic emission signals under the centrifugal pump’s cavitation states, the research was based on the centrifugal pump cavitation test. The acoustic emission technology was adopted to collect and analyze the acoustic emission signals. Four typical features were extracted, i.e. event count, ringing count, frequency centroid and root mean square. Their relationships with the net positive suction heads of the centrifugal pump were analyzed in detail. The results show that these typical characteristic parameters change obviously under different stages such as before the occurrence of cavitation, cavitation first appearing and cavitation being fully developed. They firstly fluctuate a little, then increase or decrease substantially, and then there are large reducing or increasing trends respectively. This law can be used as a technical basis for identifying the cavitation conditions of centrifugal pumps with the acoustic emission technique.