Abstract: Based on analysis of the shortcomings of oven test technology, this paper proposed a way of measuring the air moisture in the oven to understand the dry state of fiber material to be tested according to the fiber moisture absorption equilibrium. A test system was designed, and the moisture regain of fiber materials were tested. The regression equation governing the air moisture in the oven and the moisture of the fiber being dried was worked out from the obtained moisture regain of the 9 fibers. The regression equation provides a basis for determining he dry state of the fiber material to be tested by the air moisture in the oven.