Underwater wireless optical transmission adopts blue-green laser with the advantage of fast and real-time, playing an important role in ocean exploration and communication. However, the divergence of the beam itself is affected by the absorption and scattering of water, resulting in energy loss and weak signal at the receiving end. As a result, a beam shaping module based on Hadamard encoding algorithm is proposed in this paper to improve the transmission efficiency of beam in water. The wavefront phase of incident beam is modulated by liquid crystal on silicon to find the optimal hologram in multiple iterative process and reduce the loss of light energy after passing through the underwater channel. The beam is divided into reference beam and modulation beam and the angle of the two beams can be calculated by four-step phase shift. The results show that the energy of the receiver at different distances can be improved, reaching a 2.3 times increase in the energy of the receiver at 15 m. The finer the beam is modulted, the better it focuses.