The invention provides a multi-UUV (Unmanned Underwater Vehicle) cooperative system underwater target tracking algorithm for a fuzzy adaptive interacting multiple model (FAIMM). Firstly, according to the bearing-only target tracking principle of the multi-UUV cooperative system, a discrete nonlinear state and observation equation for the target tracking system is built; then, according to the characteristics of underwater target motion, in combination of five kinds of target motion modes, analysis is carried out according to the dynamic state transition matrix, the coupled inequality relation among the five modes is put forward, and a motion mode set adapted to underwater target tracking is selected optimally; then, an intermediate Gauss distribution function is adopted as a membership function, a mode probability is used as an evaluation index for filter information and corresponding covariance acquired by each mode, and fuzzy reasoning for the mode transition probability is designed; and finally, the FAIMM algorithm is designed and realized. During the multi-UUV cooperative system bearing-only target tracking process, the least number of target motion sets is selected, adaptive change of the mode transition probability is realized through the fuzzy reasoning, disordered competition among the modes are reduced, the filter accuracy is higher, and demands of multi-UUV cooperative system underwater target tracking can be met.