High-power narrow linewidth fiber lasers have played an important role in the fields of coherent synthesis, spectral synthesis, and nonlinear frequency conversion, attracting extensive attention from domestic and foreign researchers. In recent years, the fiber laser technology group (FLTG) of Wuhan National Laboratory for Optoelectronics (WNLO) at Huazhong University of Science and Technology has been conducting excellent research on domestically manufactured high-power narrow-linewidth linearly polarized fiber laser technology. In 2022, the research team achieved a 1.2 kW narrow linewidth linearly polarized fiber laser output based on a forward-pumping structure and a 3.2 kW narrow linewidth linearly polarized fiber laser output based on a counter-pumping structure, respectively, adopting a fiber oscillator laser (FOL) seed and the homemade polarization-maintaining Yb-doped fibers (PMYDF). Recently, the research team achieved a 4.1 kW narrow linewidth linearly polarized fiber laser output by applying the combination of an optimizing doped component PMYDF and an improved FOL seed for suppressing the TMI and stimulated Brillouin scattering (SBS) effects during the power scaling.