Single-frequency fiber lasers have attracted extensive attention due to distinctive laser properties on narrow linewidth, low noise, as well as preferred all-fiber structure with good beam quality, high compactness and free of maintenance, which can find widespread applications from advanced scientific research to practical applications including cold atom physics, high resolution spectroscopy, gravitational wave detection, long-distance coherent communications, and so on. Along with the rapid development of fiber laser technique, the performance of single-frequency fiber laser has been improved significantly in the last two decades and the related basic techniques have been built up systematically. Recently, a series of creative research works have been demonstrated in the area of high-performance single-frequency fiber lasers, where impressive progress has been made on newly developed mechanism and structure for single-frequency laser generation, performance improvement on laser power increment, linewidth narrowing, noise suppression as well as operation wavelength extension. Therefore, the research progress on high-performance single-frequency fiber lasers in recent five years was reviewed to reveal current trend in this area as well as the new bottleneck so as to point out the prospect on possible development routine in near future.