Polarization controlling is crucial to increase the accuracy of the fiber-optic gyroscopes. In this paper, a new method and testing device measuring the polarization characteristics of the optical components such as SLD light source, polarize maintain fiber, coupler and polarizer was introduced. This system has good qualities of low cost, easy to operate, high accuracy. Extinction ratio of fiber components can be tested up to 55dB. Tested with that device, Panda PM fiber’s extinction ratio is 25dB.