Fiber Ring Laser Gyroscope (FRLG) is a novel resonant gyroscope which uses erbium-doped optical fiber as the gain medium and optical fiber as the ring resonant cavity. FRLG have advantages over conventional Interferential Fiber Optical Gyroscope (IFOG) with its simplicity in both the optical configuration and the electronic signal processing. The precision of FRLG depend on the linewidth of fiber ring laser output. So how to get narrower laser linewidth is key technology for FRLG. According to recently report, FRLG's laser linewidth reach 100 kHz, can not directly applicable to rotation sensing at present. A Stand-wave in the un-pumped erbium-doped fiber can induce self-written fiber grating, which have self-adaptable narrow band pass characteristics. Base on this, we propose a novel FRLG's structure. Two filter sections were used in this structure to make sure FRLG run in narrow linewidth and single mode. Fiber circulator, un-pumped erbium-doped optical fiber and Bragg grating (FBG) as the reflect mirror make up of the filter section. In this paper, we have optimized the parameters through a computing simulation. The theoretical and experimental study on FRLG has been finished. We get experimental results from them. FRLG which use this structure can get bidirectional laser output, the linewidth of laser can reach about tens kHz level and the power of laser output can reach 1dbm.