The underwater trajectory measurement is an important part of the underwater warfare weapon test. First, the underwater trajectory is obtained by utilizing the target navigation noise measured by vector hydrophones, based on the principle of the vector hydrophone, with the digital signal processors to analyze and process the vector signal. The principle of the vector hydrophone and the pure location positioning principle of the vector buoy are discussed. Then, the pressure and the particle velocity phase difference of the vector hydrophone are corrected through the anechoic tank test in the laboratory, and the error in direction is rectified in the lake experiment. Using a combination of the DGPS surface orientation and the acoustic positioning, a measurement system is developed, and the three main components of the measurement system and their functions are presented. Finally, in the actual sea test, the two-dimension trajectory measurement method for the underwater warfare weapon based on vector hydrophone is shown to feature good real-time capability, high accuracy, easiness to use, and it can meet the practical requirements in operations.