The invention relates to fish culture, in particular to a micro-ecological feed additive for enhancing the color of pet fish and a preparation method thereof. The micro-ecological feed additive of the invention comprises the following components in parts by weight: 1-3 parts of candida utilis, 1-3 parts of enterococcus faecalis, 1-3 parts of lactobacillus acidophilus and 1-3 parts of bacillus subtilis; and the components are cultured in a culture medium until the pH value is 2.5-3.5 to obtain the feed additive. The product of the invention has rich nutrients and is green and environment friendly, and has good effects on the adjusting and control of the water quality in the process of culturing the pet fish and the healthy growth of the pet fish.