The invention relates to antioxidative yoghurt and a preparation method thereof. The antioxidative yoghurt comprises jam prepared from one or more of purple sweet potato, purple yam and purple carrot, wherein the jam content accounts for 8 to 15 percent of the total weight of the yoghurt. The invention also provides a preparation method of the antioxidative yoghurt. The antioxidative yoghurt provided by the invention is a milk product with excellent health-care effect, combines nutrients of the milk and the health-care effect of the purple sweet potato, the purple yam and the purple carrot, and has important auxiliary effects of improving the antioxidative function of an organism and preventing diseases.