As pump station, fiber-coupled diode laser source is one of the key elements of fiber laser, its performance restricts the output level of the fiber laser directly. Aimed at a multi-mode fiber of 105 μm core diameter and 0.22 numerical aperture, a 260 W-level high-brightness fiber-coupled diode laser model based on single-emitter-COS (chip on submount) is developed. In the design, volume Bragg grating (VBG) is used to control the spectrum of the corresponding emitter at a narrow bandwidth (about 0.5 nm), and the beam shaping technologies, polarization multiplexing and aspherical lens are taken to couple the 18 LD beams into the multi-mode fiber. The experiment indicates that, the beam shaping system can couple the 18 LD beams into the fiber, and the output power can achieve 264 W, with the E-O efficiency of 52% at operation current 18 A. Simultaneously, the central wavelength of the model is locked at 975.92 nm with an FWHM of 0.51 nm. This design offers a feasible approach to the spectral-controlled fiber-coupled diode laser. The engineered fiber-coupled diode laser system can be widely used in fiber pumping and many other areas.