The current fishery aquaculture monitoring equipment is low in endurance， high in cost and difficult to be widely used. An autonomous underwater vehicle AUV for fishery moving and fixed-point monitoring is proposed and designed. The AUV adopts a three-body modular structure design， with three Myring shaped cabins distributed in a balanced three-cabin shape to facilitate bottom stabilityand connected by T-brackets to reduce resistance. Considering the resistance interference between the three cabins of the three-body structure， the resistance calculation and design of different cabin spacing are carried out based on the computational fluid dynamics method. With the optimization objective of minimizing the direct navigation resistance， the parametric models of three cabins and the T-shaped bracket are established. The control of the AUV shape is realized by changing the parameters of the bow and stern curve equations of the cabin and the cross-section curve equation of the T-shaped bracket， which in turn leads to the shape optimization design of the AUV. The results show that the T-shaped bracket reduces the direct navigation resistance value by 26.28% compared to the traditional triangular bracket， and the AUV shape optimization reduces the direct navigation resistance value by 24.05%， which improves the endurance. The results of the study provide a new equipment in the field of fishery aquaculture monitoring， as well as a reference for the optimized design of other three-body structure AUVs.