Abstract: The Linnan depression is a center of hydrocarbon generation in the Huimin sag. The Linyi fault, as the master fault of the Linnan depression, plays an important role in the migration and accumulation of oil and gas. Therefore,it is critical to reveal the sealing capability of the Linyi fault. The factors that affect the fault sealing mainly include the geometry and mechanical property of the fault, the normal stress to the fault plane, the litholoy on the two sides of the fault and the shale smear ratio. In this paper, we used the method of fuzzy mathematics to quantitatively evaluate the fault's sealing capability so as to find out the major control factors. Results show that mechanical property is the most important factor, and the lithology on the two sides of the fault and the shale smear ratio are the second. The Linyi fault is in general well closed, but there is difference in different strata and places. According to our calculation, the Shahejie Formation is the best one in terms of sealing condition, the Guantao Formation the second and the Dongying Formation the worst. In space, the sealing condition is better in the west.