The complex environment of high sea conditions will lead to dynamic misalignment of the magnetic coupling structure of the underwater vehicle wireless charging, which can cause the charge of key parameters such as mutual inductance and reflection impedance, and lead to the decline of the efficiency and stability of the wireless charging system. To address this problem, a bidirectional wireless power transfer (WPT) system with input-series - output-parallel (ISOP) connection is proposed. This system is characterized by strong anti-misalignment in various directions under phase-shift control. Based on a clear understanding of the system’s operating principle, the design methods of the arc-shaped coupler and compensation parameters are carried out. Finally, a 1 kW underwater bidirectional WPT prototype is built to verify the feasibility of the proposed solution. Experimental results show that the axial misalignment distance is [−60 mm, 60 mm] and the angular misalignment is [−20°, 20°].