Abstract: In the report，based on the CFD （computational fluid dynamics） method， a numerical model of the interaction between waves and ballast-type floating breakwaters was established， the wave field distribution characteristics were simulated and analyzed， and the effects of liquid sloshing in the ballast tanks on the wave attenuation performance of the floating breakwaters were explored. The results showed that the ballast-type floating breakwaters improve the wave attenuation performance through reducing the motion response of the breakwaters and increasing the consumption of incident wave. Compared to the dry sand-type floating breakwaters， the wave attenuation performance of ballast-type floating breakwaters can be improved by up to 21.9%. When the incident wave frequency is close to the natural frequency of the liquid sloshing in the tank， the resonance occurs within the tank， leading to a reduction in wave attenuation performance. By adding vertical baffles inside the ballast tanks to change the natural frequency of the liquid sloshing， the wave attenuation performance of the breakwaters can be improved by up to 51.6%. These results are expected to provide new ideas and solutions for the field of coastal protection engineering and offer some references for the practical engineering.