Large cage net (purse net) is a vital way to utilize the sea water resources of deep sea.Net damage detecting is the basic condition for its normal running. Low cost and high reliable frame-type AUV is a feasible technical method to conduct the function. Based on the requirement of technique, cost and convenient operation, this paper proposes a cage net spiraling detection strategy of frame-type AUV, sets up the motion model and computes the driving force.The control method and working conditions relative with water current etc. were obtained. According to the model analysis, this paper designs the frame-type AUV structure, develops the 3 degree of freedom control hard/software and underwater video supervising/microwave communication system with 1.5 km working distance. The equipment developed is verified in Xiangshangang Bay of Zhejiang Province, China. The results show the system can acquire clear cage net pictures within 0.9 m and 1.5 m distance in spring and neap tide respectively from underwater when the flow velocity is less than 0.8 m/s, and its damage situation can be easily judged, which meets the practical requirement and provides stable foundation for large scale application.