To realize the target spectrum matching of CIED65 standard illuminant and AM1.5 standard solar spectrum by employing monochromatic LED, a simple genetic algorithm as the spectral matching algorithm was proposed, by solving nonnegative least square solution of overdetermined equations, the combination of monochromatic LED light source with different peak wavelength, peak wavelength interval and full width at half maximum was optimized, and the light source spectral matching was achieved. Simulation results show that the fitting correlation index is above 0.99, the fitting spectrum is consistent basically with the target spectrum. The smaller the interval of spectral matching peak wavelength is, the better the spectral fitting effect is, to meet the needs of engineering application, the peak wavelength needs to be selected moderately. The proposed algorithm runs fast, has high efficiency and small fitting error, and it can be widely used in the spectral matching simulation test and engineering practice for special lighting fields such as plants lighting, medical lighting and so on.