To overcome the shortcomings of the optical fiber coupling of a domestic higher power diode laser, an optical fiber coupling focusing system was designed and a 5 kW optical coupling diode laser was developed. The optical fiber coupling methods by common circle spot and diode laser squarespot were compared. For a domestic array diode laser stack, the optical quality homogenization, polarization beam bunching, multi-wavelength bunching were used to increase the energies, by which the laser can be coupled into the optical fiber with a core diameter of 800 μm and a Numerical Aperture(NA) of 0.2. Thus, the fiber coupled output power reaches 5 109 W, the fiber coupling efficiency is 85.69%, and the electro-optic conversion efficiency of overall system is 49.48%. Moreover, the power density reaches 2×105 W/cm2 when focal length is 250 mm. The laser has been used in multi-wavelength surface remelting, metal alloying, laser cladding and laser welding fields. All the parts of the laser are made in China except the optical fiber for energy transfer, so it promotes the progress of higher power domestic optical fiber coupling lasers.