Abstract: A very long baseline wideband passive localization method based on distributed buoy network for accurately measuring 3D vertical climbing trajectory was presented.Four buoy nodes distributed squarely are considered in this paper.Horizontal position x and y can be estimated by use of the localization methods based on azimuths crossing. Azimuth estimation can be obtained using smart acoustic vector sensor instead of conventional antenna.A result from a lake test shows that azimuth estimation error is lower than 0.4 deg.And vertical position z can be extracted from TDD (Time Delay Difference) between direct and surface reflect paths,and give on-sea test results for climbing mobile target with high speed,which shows that trajectory measurement error is lower than 10 m.