An automatic fiber cleaning system comprises a first cleaning module, a second cleaning module, and a sprayer. Each of the first cleaning module and the second cleaning module has a cleaning belt, a driven belt wheel on which an unused portion of the cleaning belt is wound, a driving belt wheel on which a used portion of the cleaning belt is wound, and a pressing tool on which the cleaning belt is tightened. The sprayer sprays a cleaning agent onto the cleaning belts. The pressing tools press the cleaning belts on both sides of an optical fiber and clamp the optical fiber. The cleaning belts move relative to the optical fiber by the driving belt wheels to wipe the optical fiber.