Abstract: The repetition positioning precision from USBL system produced by Sonardyne Co. is investigated by pool and lake experiments. The aim of the experiments is to verify whether the USBL system can be used in the process of ROV dynamic positioning. The experiments results have shown that the USBL system has given an acceptable repetition precision with gesture dynamic compensation even if the pitch and roll of the support vessel actually exist. And the USBL system can be used for ROV dynamic positioning.