The crystal structure and stability of H type gas hydrate were studied by using molecular dynamics simulation method for the first time.Site-site pair radial distribution functions for H type gas hydrate were determined The influence of temperature and guest molecule on the stability of crystal structure was investigated by computation of translational mean square displacement

orientational mean square displacement and orientational autocorrelation function for water molecules. It is found that the stability of hydrate crystal depends upon the guest molecule enclathrated in the cavities.On the other hand，the influence of temperature on the stability of crystal structure is insensitive.