Autonomous Underwater Vehicle (AUV) is an intelligent machine that works at hazardous underwater environment. It can only operate for hours or days at a time by battery charging system. This paper presents a new gyroscopic charging system to reform the traditional way. The new system utilizes the gyroscopic effects of a large rotating flywheel in combination with a controlled power take-off device to extract power from wave motion. In this paper, a gyroscopic energy converter model is given, which contains a description of dynamic equation and controlling design. Consequently, a detailed process of applying the gyroscopic system to a typical AUV is shown. The gyroscopic charging system promises to reduce AUV battery requirements negating the necessity to carry sufficient energy reserves (size and weight) for entire missions, reduce costs by freeing support vessel time (a major cost component in AUV deployment) and enable AUVs to be remotely and renewably recharged at sea, indefinitely extending missions. Software simulation is the main method to prove the validation of the results. The results show that the generated power is sufficient to provide power for AUV which is better than the battery charging system.