Abstract: This study aimed to research the technical formula and antioxidant properties of mixed freeze-dried food prepared using kefir quinoa fermented milk, sea buckthorn puree, yellow peach thick pulp and carrot thick pulp as raw materials. The optimum process formulation of mixed freeze-dried food was determined by single factor test and orthogonal experiment using sensory score and solid content as evaluation indicators. Subsequently, the contents of flavonoids and polyphenols and the dynamic changes of DPPH free radical scavenging rate, hydroxyl free radical scavenging rate, superoxide anion free radical scavenging rate and iron reducing power of mixed freeze-dried food were investigated after lyophilization and in vitro gastrointestinal digestion. Results showed that the optimal mass ratio of kefir quinoa fermented milk, sea buckthorn puree, yellow peach thick pulp and carrot thick pulp in mixed freeze-dried food was 50 ∶13 ∶30 ∶10. Under this condition, the solid content was 19.9%, sensory score was 81.4 and comprehensive score was 63.0. Besides, the contents of flavonoids and polyphenols in mixed freeze-dried food were both increased, and the DPPH free radical scavenging rate, hydroxyl free radical scavenging rate, superoxide anion free radical scavenging rate and iron reducing power were significantly ascended after digestion（P＜0.05）.