The purpose of this work is to research the spill and diffusion characteristics of liquid hydrogen in confined cabin with air supplying and vent. The spill and diffusion behavior of liquid hydrogen in the confined cabin with air supplying and vent was simulated using Fluent software. The feasibility of the model was verified by the experimental results. The research results show that the numerical simulation model can simulate to predict the diffusion process of liquid hydrogen well and has application value for engineering. The diffusion cloud after the spill of liquid hydrogen is gathering at the top and slowly spread to the surrounding which is different from the open environment. The process of liquid hydrogen spill can be divided into three stages, among which the concentration of cloud clusters changes sharply in the spilling stage. Low wind speed can affect the inclination angle of the diffuse cloud, and it is concluded that wind speed is also the main factor affecting the movement of the diffusion cloud. The research results are expected to provide a reference for standard formulation and design of liquid hydrogen applications.