Abstract: Navel orange could protect the color in compound juice of yacon and navel orange, because it could inhibit the activity of polyphenol oxidase. The color-protection effects of navel orange, ascorbic acid (VC) and citric acid on compound juice of yacon and navel orange were studied. And the optimum combination of navel orange and composite color protection agent was investigated by orthogonal test. Fuzzy mathematical sensory evaluation was applied to compound juice. The results showed that the color protection effect of composite color protection agent combined with navel orange was better than single. The best ratio was 0.02% VC, 0.3% citric acid, 15% navel orange. The result of fuzzy mathematical comprehensive evaluation was excellent. And it verified that sensory quality of the compound juice was good, and it would be accepted by consumers.