The generation of hydrate has brought a lot of difficulties in processes such as gas extraction, gas gathering and so on. The establishment of forecasting model is a puzzle in hydrate prevention and cure. The advantages and disadvantages of four commonly used forecasting model are summarized. The statistical thermodynamics principle is used to establish gas hydrate forecasting model, and five main factors that affect gas hydrate formation are analyzed, including the gas composition, temperature and pressure, ion concentration, acidic gas and inhibitor added. This forecasting model is applied in Luojiazhai gas reservoir, and the result shows that the predictive values are consistent with the experimental results. The establishment of gas hydrate forecasting model is significant for hydrate prevention and guiding gas production.