Abstract: To study the influence of fences on the symmetric shift of the flammable region at a leakage and diffusion process of liquid hydrogen, a 3D transient CFD model was established based on the NASA large-scale liquid hydrogen release experiments, and the distribution of the flammable region and the symmetric shift law without fences, with a half fence in the downwind direction, and with a full fence were comparatively analyzed. The results show that the reason for the symmetric shift of the flammable region comes from the entrainment of the hydrogen cloud to the air along the path. The flammable regions form bifurcated structures the earliest when there is no fence, under the half fence and no fence conditions, small plumes form between the bifurcated structures. Regardless of the fence type, the volume of the flammable region continues to rise for 12 s after terminating the liquid hydrogen release to the maximum value of about 30000 m³. The volume of flammable region in the case of no fence and half fence has been reduced to 0 at the 80 s, while in the case of a complete fence, due to the vortex near the half fence in the upstream direction, there remains a residual flammable region of 4.6 m³, which is a potential problem that needs to be paid attention to in the actual hydrogen energy application scenarios.