To achieve spectral combining of multiple-wavelength beam array based on reflective diffraction grating, a home-made reflective diffraction grating coated with gold film is used as a dispersion element to achieve spectral combining of two single-mode laser beams with wavelength of 1064 nm and 1080 nm. The structure of the combination system and the optimization method for the beam quality are studied. The combined power of 13.64 W, combined efficiency of 91.9% and combined beam quality of 1.53 are achieved. The beam quality degradation and its influence factors in dispersion plane are estimated.