For the detection of high pressure hydrogen leakage and diffusion, domestic and foreign scholars have carried out relevant research by using experiment and numerical simulation, and put forward some detection methods. These detection methods have reliable results, but generally have the shortcomings of slow response. In this paper, a fast visual detection method of high pressure hydrogen leakage based on light sheet is proposed. The laser is emitted by a semiconductor laser, and a laser sheet is formed after passing through a cylindrical lens group and a mirror. The high-pressure hydrogen leakage was identified after digital image processing. Based on this method, the layered flow model of high-pressure hydrogen jet is established. The experimental results are consistent with the previous experimental formula, which proves the feasibility of the method; the simulation experiments of 3, 5, 7 MPa pressure when the leakage diameter is 1 mm, and 0.5, 1, 1.5 mm leakage diameter when the pressure is 5 MPa are carried out The analytical relationship between the diameter of high pressure hydrogen leak and the specific height, the diameter of gas jet boundary layer, and the analytical relationship between the pressure of high pressure hydrogen and the diameter of jet boundary layer are obtained by the simulation experiment, which provides a strong support for the rapid and accurate detection of high-pressure hydrogen leakage.