In recent years, fiber laser has been developing rapidly, and gradually applied in many fields. Further improvement of output power is still the research hotspot of fiber laser. Beam combining is an important method to scale output power of fiber laser. Beam combining requires that the sub beam is a narrow linewidth fiber laser, so the research of narrow linewidth fiber laser is of great significance for power improvement. In this paper, the development and research status of narrow linewidth high power fiber lasers are introduced in detail, and based on the current research status, the future development trend is prospected.