The utility model discloses a device for on-line surface cleaning monitoring and processing of an optical element, which comprises an optical element surface particulate matter on-line detection system, a dark field imaging system of the optical element surface particulate matter on-line detection system is positioned above the optical element and is vertical to the optical element; The cleaning treatment device is used for cleaning the optical element and realizes the position movement of the wiping mechanism through the horizontal movement mechanism and the vertical telescopic mechanism so as to wipe the surface of the optical element; And the upper computer is in communication connection with the optical element surface particulate matter on-line detection system and the cleaning treatment mechanism. The device provided by the utility model can be used for carrying out real-time on-line monitoring on the surface of an optical element; and meanwhile, very timely cleaning treatment iscarried out according to the dark field monitoring result, the operation is simple and convenient, and the risk of secondary pollution caused by manual operation is also avoided, so that the damage to optical elements is reduced, and the stable operation of the high-power solid laser device is effectively ensured.