Objective: this study focuses on developing a kind of sugar-free fermented milk with beneficents to health. Methods: quinoa pulp was added to the reconstituted milk, with xylitol used to replace sucrose. The physicochemical properties, including acidity, viscosity, water holding capacity and in vitro antioxidant were measured to explore the effect of quinoa pulp on sugar free fermented milk. Results: the pH of fermented milk with quinoa pulp was higher than that of ordinary fermented milk, while the acidity, viscosity and water holding capacity were slightly lower than that of ordinary fermented milk. The DPPH radical scavenging rate (86.23%), ABTS radical scavenging rate (71.32%), hydroxyl radical scavenging rate (63.27%) and Fe³⁺ reducing capacity (0.48 mmol/L) of the sugar-free fermented milk was higher than those of ordinary fermented milk. Conclusion: it is proved that the addition of xylitol and quinoa pulp can change the physicochemical properties of fermented milk and improve the antioxidant activity of fermented milk, which can provide some theoretical support for functional fermented milk.