Aiming at the problem that it is difficult to detect underwater targets quickly and effectively, the acoustic tomography method is used to observe the wake distribution of underwater targets in the domain and its evolution process with time, and the detection of underwater targets is realized through the change of flow field. The experiment of simultaneous acoustic transmission at 5 stations of coastal acoustic tomography (CAT) is carried out, and the two-way acoustic propagation time data are obtained, and the flow field distribution is inverted; Three-dimensional inversion method is used to observe the evolution process of the horizontal flow field at the depth of the autonomous underwater vehicle (autonomous under water vehicle, AUV), and the inversion results are basically consistent with the path-averaged velocity calculated directly; During the experiment, the flow field of the underwater vehicle was obviously fluctuated, and the acoustic Doppler current profiler (acoustic Doppler velocity profiler, ADCP) and CAT observations were 1. 57 m/s and 1. 43 m/s, respectively. The results show that the success of using CAT method to observe and detect AUV targets in small-scale areas lays a foundation for the follow-up observation experiments.