Abstract: To solve the problem that the conventional PVT techniques in the evaluation of hydrate formation demand for large equipment and feature in long experimental period and poor precision, a new DSC technique evaluating the gas hydrate inhibition in deep water drilling fluid is developed. Based on understanding the gas hydrate formation environment, the damage to the deep water drilling and the conventional evaluating methods, utilizing the functions of the high pressure microcalorimeter, the rule of gas hydrate generated from methane in different liquid medium is studied. The evaluating method of the gas hydrate inhibition is established. Finally the case study of the DSC technique used to evaluate the gas hydrate inhibition of saline and deep water drilling fluid is given. Research shows that the drilling fluid hydrate inhibition can be measured quickly, conveniently and exactly by using the high pressure microcalorimeter. The measuring results are the same with that of the traditional one. The deep water-base drilling fluid system evaluated has good hydrate inhibition.