A flash sterilization structure of a water dispenser comprising an outer housing (10) having an inlet (11) and an outlet (12), and an Ultra-Violet (UV) lamp (40), and the flash sterilization structure characterized in comprising:a reflection tube (20) mounted in the outer housing and having a tubular member (21) havingan inner surface being light reflective； andtwo opposite ends； anda flowing chamber (22) defined in the tubular member and through the ends of the tubular member, and communicating with the and the outlet of the outer housing；a quartz tube (30) mounted in the reflection tube, and having an outer surface facing the inner surface of the tubular member, wherein the UV lamp is mounted in the quartz tube； anda helical member (50) made of metal, being circular in cross-section, mounted in the flowing chamber of the reflection tube, coiled between the reflection tube and the quartz tube, extending between the two ends of the tubular member of the reflection tube, and abutting on the inner surface of the tubular member and the outer surface of the quartz tube, such that a helical flowing channel (51) is formed between the tubular member and the quartz tube.
