The quantities prediction is an important part of fishery resource assessment and aquaculture.Traditional active sonar and large-scale fishing gear trials and other methods have certain defects.For the quantitative assessment of freshwater fish,the hydroacoustic signals of bream and crucian carp in the same proportion and different mixed quantities were collected by hydrophone and acoustic recorder.54 characteristic parameters were extracted and used for correlation analysis.The characteristic parameters significantly correlated with the mixed quantities of freshwater fish were selected.The Rank-RS method was used to divide the samples.The multiple linear regression model was established and compared with the prediction effect of the partial least squares regression model.The results showed that the correlation between the average Mel frequency cepstrum coefficient and mixed quantity of freshwater fish was the most significant on the whole.The fitting effect of the multiple linear regression model was better.The prediction model R〖DD(-*2〗—〖DD)〗2 and the RPD was 0.950 and 4.492,indicating that the established model was suitable for predicting the mixed numbers of freshwater fish.It is feasible to apply passive underwater acoustic technology in studying quantities of freshwater fish.