The flammable vapor cloud formed by liquid hydrogen spill can severely threaten the safety of life and property, which is one of the primary concerns during handling liquid hydrogen. Mixture model and Realizable k-epsilon model are adopted in ANSYS Fluent to predict the two-phase flow of liquid hydrogen spill. Dilution of the hydrogen vapor cloud formed by liquid hydrogen spill is analyzed, including the turbulent disturbance during cloud dispersion, and the cloud dilution characteristics especially its behavior under different wind speeds. The results show that the turbulent disturbance in the upper part of flammable vapor cloud can be 7.21 times of that in the background atmosphere, due to the mixing of the vapor cloud with the incoming wind and the upper air. The dilution time, needed for the vapor cloud to be diluted below the lower flammable limit since the end of the spill, increases firstly and then turns to decrease with the increasing wind speed. The atmospheric turbulence, the turbulent disturbance induced by the upward movement of vapor cloud, and the cloud frontal area all affect the dilution behavior. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.