A UV sterilization system with autocleaning structure comprises scrubbing collars, at least one cleaning liquid box and at least one sliding bar. Said cleaning means further comprises at least one towing bar, at least one sliding bar and at least one supporting bar. The boxes are vertically mounted on or fixed to the supporting bar(s) to form together with the supporting bar(s) a rectangular shape. A cleaning liquid addition port and a cleaning liquid drain port are respectively provided at the top and close to the bottom of each cleaning liquid box. Said cleaning liquid addition port is connected with a cleaning liquid supply pipe and the cleaning liquid drain port is closed by a detachable sealing member. Several sets of holes with the same diameter for scrubbing collars are provided on the opposite sides of each box with each set at the same height. Each UV lamp is separately installed within a protective sleeve passing through the scrubbing collars. Each towing bar is fixed to the outside of the cleaning liquid box and is connected with the sliding bar and the piston rod of the driving device. The present device according to the invention can be used for the sterilization of fluid such as sewage, tap water, etc.