Objective: Liquid hydrogen, owing to its remarkably high specific energy and broad application prospects has attracted widespread attention in research and development, particularly in aerospace propulsion and sustainable clean energy storage and transport. However, the practical large-scale use of liquid hydrogen faces notable and demanding safety challenges. Liquid hydrogen has an exceedingly low boiling point; once a leak occurs, it rapidly vaporizes to form a hydrogen cloud. At flammable concentrations, this cloud can ignite or even explode upon encountering a flame or a static spark, posing serious safety hazards. Therefore, an in-depth investigation of liquid hydrogen leakage, diffusion, and vaporization behavior in open environments is crucial for devising effective safety protection strategies and emergency-response mechanisms. Owing to the inherently high risk, technical complexity, and substantial economic cost of liquid hydrogen experiments, publicly available data on liquid hydrogen release remain extremely scarce, severely limiting further progress in this field. Methods: To address this research gap, a large-scale open-environment liquid hydrogen release experiment was executed, aiming to systematically obtain the diffusion characteristics and evolution process of the released liquid hydrogen. For this purpose, a comprehensive experimental platform was built, integrating a liquid hydrogen storage and release system, a sensor-array system, a remote monitoring and control system, and video and infrared observation systems. This platform collects key parameters in real time—including hydrogen volume fraction, temperature, wind speed, and wind direction—and records the hydrogen cloud evolution from multiple angles, ensuring thorough experimental data acquisition. By fully considering diverse environmental and operational parameters—such as wind speed, ambient temperature, release angle, ground-cover type, and release flow rate—the experiment completed 12 sets of valid release conditions. Results: Given the large data volume, this study focused on presenting the detailed results and analysis of the second release experiment. During this experiment, multiple high-definition cameras were placed on the ground, and gimbaled aerial cameras captured the real-time spatial distribution of the hydrogen cloud from multiple perspectives. moreover, the sensor array recorded the dynamic changes in the hydrogen volume fraction at each measurement point. Based on these data, the liquid hydrogen release process was divided into four characteristic stages—ground spread, buoyant transition, stable plume, and cloud dissipation—and the evolution features of each stage were systematically summarized and analyzed. For the quantitative analysis, the sensor data were used to track the hydrogen cloud movement. Furthermore, this study employed the open-source computational fluid dynamics (CFD) code OpenFOAM to perform three-dimensional, transient numerical simulations under the second experimental condition. The deviations between the simulated results and experimental observations fell within acceptable tolerances. Conclusions: This study not only provides large-scale experimental data on liquid hydrogen leakage in open environments—offering valuable foundational data for subsequent research—but also provides robust theoretical support through advanced CFD simulations coupled with empirical experiments. The integrated findings hold considerable reference value and practical importance for advancing the safe, reliable, and sustainable development of the hydrogen energy industry worldwide.