Aiming at the shortcomings of the design of the underwater laser peripheral scanning ring window, a design method of the transmitting optical system that shifted the scanning base point was proposed. This method was based on the structure of Kepler telescope. The divergence angle of the beam and its distribution uniformity were optimized by adopting the image-side telecentric method for the conjugated design and distortion control of the objective lens and the eyepiece group. On the basis of the optimized design, the influence of the flat window and the conformal window on the beam quality and the influence of the coating on the energy transmission efficiency were simulated and analyzed respectively. Finally, tolerance analysis and hydraulic simulation of different window designs were carried out. The simulation results of optics and mechanics show that the method effectively reduces the window area of the shell surface, avoids the blind area of the fan-shaped detection caused by the design of the ring window, and has certain guiding significance for the engineering design of the underwater laser peripheral scanning emission system.