FSC series high-power single-mode continuous-wave fiber laser is developed and produced by Beijing Reci Laser Technology Co., Ltd. The average power exceeds 4000W with single resonant cavity and single-mode beam quality by solving the obstacle of transverse mode instability (TMI), stimulated Raman scattering (SRS) and poor beam quality. This series products can be widely used in fine cutting, metal welding, surface treatment, 3D printing and rapid prototyping, due to the high average power, multiple anti-high-reflection, high beam quality, and high electro-optic conversion efficiency.