With the development of ocean engineering and demand for safety of the ship and offshore structures,the transportation and storage of liquid have become an important issue nowadays.Furthermore,in order to improve the hydrodynamic performances of the ship and offshore structures,the anti-rolling liquid tanks are often taken into consideration.The internal-external coupling flow effect is vital for the ship and liquid tank designs,especially when the external wave frequency is close to the natural frequency of liquid tanks with a certain filling ratio,large amplitude motions may occur,which is dangerous to some extent.In this paper,the simulation-based-design method is introduced at first,and the verification of the numerical calculation of internal-external coupling flow with liquid tanks is done then.Finally,the filling ratio of the anti-rolling liquid tank and the installation angle of the anti-rolling fins are optimized to reduce the roll motion amplitude of the hull section to the greatest extent under the combined action of the two anti-rolling devices.Optimization results show that the roll motion amplitude of box-shaped hull section can be successfully reduced by reasonably designing the two anti-rolling devices,which can be a reference to the future design of the fishing ship and other ships with anti-rolling devices.