Abstract: To solve the problem of biased estimation of vertical trajectory of underwater volume targets caused by inaccurate sound velocity measurement and deviation of attitude sensor installation, a long baseline positioning method for underwater motion volume target trajectory is presented, in which the sound velocity error and installation attitude error are jointly estimated with the motion trajectory as unknown parameters. Theoretical analysis and simulation experimental results show that the velocity error and installation attitude error mainly affect the performance of vertical trajectory estimation for volume targets. The proposed method effectively eliminates the systematical deviation of vertical motion trajectory caused by systematical error. In the sea experiment, the vertical estimation performance of the long baseline volume target trajectory estimation method is evaluated by using the pressure gauge depth measurement as the reference, and the proposed method reduces the deviation of vertical motion trajectory from 3.67 m to 0.02 m, which improves the accuracy of the vertical trajectory of underwater volume targets.