The flow of sea currents and the internal lift slurry around the deep ocean lifting system will produce fluid-structure interaction force on the flexible hose, and the 3D fluid-structure interaction model of the flexible hose with the internal slurry and external fluid was established. The spatial deformation and stress distribution characteristics of the flexible hose under the influence of internal and external fluid were analyzed. The results show that the maximum horizontal displacement of flexible hose decreases with the increase of internal fluid velocity and density, the maximum principal stress of flexible hose first decreases and then increases with the increase of internal fluid velocity, the maximum principal stress of flexible hose increase with the increase of internal fluid density, and the maximum horizontal displacement and principal stress of flexible hose increase with the increase of external fluid velocity. In order to ensure the spatial configuration of flexible hose during operation and the safety and efficiency of deep-ocean mining system, the internal fluid velocity and density should be kept within a reasonable range. The flexible hose should work with the external fluid velocity less than 0.3 m/s.