Abstract: Objective:To study the antioxidant and antibacterial activities of different extracts from the flowers of Hylocereus undatus.Methods:The ethanol, acetone and ethyl acetate extracts were obtained by cold-extraction. The antioxidant activities were studied using DPPH, ABTS assay and reducing power assay was measured.; The antibacterial activities were studied using Kirby-Bauer and tube method.Results:Different extracts from the flowers of H. undatus exhibited antioxidant activities, and the most outstanding one was found to be the ethyl acetate extract ( EAE) ; the EAE extracts from the flowers of H.Undatus had the obvious bacteriostatic effect on the typhoid bacillus and the minimum inhibitory concentration was 12.5mg /mL.Conclusion:All the extracts could be employed as natural antioxidants and antimicrobial.