The invention discloses a method for optimizing a spectrum of a multi-light-color LED. The method comprises the following steps 1, 2, 3 and 4 or 1, 5, 6 and 7 of: step 1, carrying out a method for mixing light colors of the spectrum of the multi-light-color LED; step 2, selecting and computing a synthetic chromaticity of the multi-light-color LED; step 3, computing spectral reflection efficiency of the multi-light-color LED; step 4, computing a light color effect of the multi-light-color LED after irradiating an object; step 5, selecting fitting chromaticity of the multi-light-color LED after irradiating the object; step 6, computing the light color effect of the of the multi-light-color LED; and step 7, computing the spectral reflection efficiency of the multi-light-color LED. According to the method, the spectral reflection efficiency and the light color effect are improved by virtue of a spectral optimization technology; and the method is applicable to landscape lighting, scene lighting, commercial lighting and certain functional lighting occasions and the like.