Abstract: A theoretical model of a propeller cavitation noise modulation spectrum for ships with skewed propellers is established.According to the relationship between wake velocity and cavitation noise volume,and the relationship between propeller speed and number of bubbles,the mathematical expression of the cavitation noise modulation spectrum is derived.Theoretical analysis and simulation show that the difference between the blades is the main reason for the existence of a shaft frequency line spectrum in the modulation spectrum,and that the main factors affecting the blade frequency intensity in the modulation spectrum are the propeller skew angle and speed.The results of this research provide a theoretical basis for the analysis and extraction of modulation spectrum characteristics of radiated noise,and also have a reference value for the design of propeller structures and the noise reduction of ships.