Fiber Bragg Grating(FBG) tensile fatigue property seriously affects the long term reliability of FBG strain sensors. To evaluate FBG tensile fatigue property, the package of FBG sensors is analyzed, and the surface mounting FBG is selected to study the FBG tensile fatigue property. To distinguish the tensile fatigue signal of FBG from the bonding layer, the property of the grating reflection spectrum is proposed as the evaluation index of FBG, and sensing characteristics is proposed as the evaluation index of bonding layer. The grating reflection spectrum evaluation index includes side mode suppression ratio and the 3 dB bandwidth. And the sensing characteristics evaluation index includes sensitivity, linearity and the strain transfer efficiency rate. To verify this theory, an experiment based on equal strength beam is conducted, in which the amplitude of “AC” strain is 500 micro strains, and the frequency is 18 Hz. After 10 million tensile fatigue tests on three FBG sensors, the average bandwidth increase 2.07%, the strain transfer efficiency rate decrease 4.5%, and the sensitivity decrease 3.9%. The experiment results show that this theory is workable.