Abstract: According to the acid gas field of Sichuan area, an important project of Sichuan gas field exploration and development is that how to determine hydrogen sulfide content accurately in the drilling fluids during the drilling process in the region, and by which means to remove hydrogen sulfide from drilling fluids so as to prevent its effect on the drilling operation. This paper describes the source, existing state and harms of hydrogen sulfide in drilling fluids, introduces a method of measuring hydrogen sulfide by iodometric method, and studies the influence of the adding amount of test solution. At the same time, this method has been used in several wells in Sichuan area, and the attentions of testing hydrogen sulfide by iodometric method have been summed up, which has very important meanings for the determination of hydrogen sulfide in drilling fluid.