In order to find out the reasons for the poor bending stiffness performance of plastic fishing raftand find a way to solve the problem of easy deformation. in this study, three factors affecting the bending stiffness were analyzed and compared with traditional mariculture cages: frame section, elastic modulus of frame material, and the span of the floating ball tied under the frame. Results show that there is little difference in the moments of inertia between the side section of the plastic fishing raft frame and the wooden frame of the traditional aquaculture cage, that is, the geometric properties of the cross-sectional structure are similar. The span of bound floating balls under the frame of plastic fishing raft is basically the same as that of traditional mariculture cage, and is not the main factor leading to the difference of bending stiffness. The main factor affecting the bending stiffness difference between the two is the material performance, because the elastic modulus of HDPE is about 8.18% of Hemlock which is the traditional cage frame material. That means due to material characteristics, plastic cages have insufficient rigidity compared to traditional aquaculture cages, which could easily affect the production safety. Several methods are recommended to improve the rigidity of HDPE mariculture cages, such as improving structural performance through optimization, modifying HDPE to increase its elastic modulus, and adding auxiliary rigid facilities to achieve the purpose of increasing bending stiffness.