Magnetic coupling wireless power transfer technology realizes contactless energy transmission through high-frequency electromagnetic fields. The control objectives of the wireless power transmission (WPT) include maximum efficiency control and transmission power control. The control objectives can be easily achieved through communication between the transmitting and receiving sides. However, with underwater environments, it is difficulties in achieving high reliability and high-speed wireless communication, then communication free control method would be a feasible control method. In this paper, a communication-free control method is realized by the online parameter identification techniques. The mutual inductance is identified by the neural networks and is used to estimate the optimal load impedance. Thus, the optimal efficiency control can be achieved on the receiving side and the constant power control is realized in the transmitting side. The LCC-S type wireless power transfer system is employed to build the experimental platform and the experimental results indicate that the proposed control method can realize the maximum efficiency control with a designed transmission power.