Abstract: Working principle and basic structure of a fiber ring laser gyroscope(FRLG) are described and analyzed. This FRLG system project is specified with a structure of a pumped laser with composite cavities. According to the structure of FRLG, the output of bidirectional laser can be matched by adjusting the structural parameter. Experimental results demonstrated fine responses between variation of voltage and cavity rotation rate. The minimum cavity rotation rate of turntable detected by the detector reached as high as 0.02°·s^-1.