Abstract: Based on the analysis of the influence of fiber coil on the overall performance of fiber optic gyro(FOG), we proposed to assess the quality of fiber coil by utilizing the Brillouin optical time-domain analysis (BOTDA) optical fiber sensing technology. Through the on-line testing, thermal stress testing and framework performance testing for fiber coil, we could discover and eliminate the stress spike and layering switch phenomena in time,also the optic fiber stress curve reversing induced by framework and heat stress could be removed.