Owing to the increasing demand for deep sea exploration, remotely operated vehicles (ROVs) that can conduct scientific tasks up to a depth of 6000 m are essential for exploring unknown areas. For electrically propelled ROVs, a voltage regulation system is used to maintain the load-side voltage within a limited range during power load variation. The load-side voltage fluctuated frequently during load variation, thus challenging the design of the voltage regulation system. Hence, we propose a novel voltage regulation strategy in the ship-side of a 6000-m-deep ROV system. In this strategy, the nonlinear relationship of the compensated voltage in the ship-side and the active current in the umbilical cable are solved by piecewise linear fitting using the least-squares method. Subsequently, a feedback PID controller is designed to achieve a faster dynamic response and maintain a stable load-side voltage. The real applications of the ROV system for oceanographic surveys demonstrated that the fast response and high accuracy of the voltage regulation system for intense fluctuations of the load-side voltage could be achieved.