Non-asbestos gaskets have high tensile properties, good permeability resistance, and resilience. Compared with traditional asbestos gaskets, non-asbestos gaskets have the advantages of less pollution and no harm to human body. This manuscript presented an experimental and theoretical study of aramid fiber reinforced non-asbestos gaskets. The tensile strength of gaskets with different fiber orientations and tensile rate were conducted in order to meet the industrial standard. The leakage rates of nondestructive non-asbestos gaskets with different sizes under different medium pressures and pretightening load were investigated. The results showed that the leakage rate can reach the industrial standard when the pretightening load reached 30 MPa and medium pressures was less than 2 MPa. The artificial scratch defects were made on non-asbestos gaskets, and the effect of the width and depth of the scratch defect on leakage rate was further investigated. The sealing failure would occur when the scratch depth reached 0.1 mm. The modified model containing defect factors was established. The results showed that the modified model can well characterize leakage rate of gasket.