Abstract: The formation of natural gas hydrate is harmful to the exploitation and transportation of natural gas, so it is important to accurately predict the formation conditions of gas hydrate. At present, three prediction methods named thermodynamics model calculation, formula method and image method are mainly included. The formula method has got much attention with the character of easy calculation which is applied conveniently in engineering. In view of this, eight calculation equations are presented. Through the known pressure calculate temperature and the known temperature calculate the pressure, the calculated values of hydrate formation conditions are compared with the experimental values for the sweet natural gas, sour gas with the high component of CO₂ or H₂S. When the temperature of hydrate formation conditions is calculated by the pressure, for the sweet natural gas, the minimum average relative deviation is got by Hammer and is recommended to calculate hydrate formation conditions. For sour gas with the high component of CO₂, Bahadori method is recommended to calculate hydrate formation conditions. ZahediⅠmethod is recommended to calculate sour gas with the high component of H₂S. When the pressure of hydrate formation conditions is calculated by the temperature, it is found that small average relative deviation is got only by Towerl method, Bahadori method and Hammer method for the sweet natural gas. Neither of the methods is suitable for sour gas with the high component of CO₂ or H₂S.