The invention discloses an alternate treating device of decontaminating filter screens for an open channel, and relates to a decontaminating device. The filter screens are respectively embedded in the upper part and the lower part of a frame, a power motor I is arranged at the top of the frame, the power motor I is in transmission cooperation with chain transmission mechanisms on outer walls on both sides of the frame, and the chain transmission mechanisms drive a sliding beam to move in slide grooves in both sides of the frame; suspension hooks and pushing hands are fixed below the sliding beam, the suspension hooks grasp lifting handles at the upper ends of filter screens, and the pushing hands are propped against the lifting handles; a funnel is hinged to the sliding beam through a suspension arm and positioned on one side of the frame, and a triggering lock device is arranged at the hinged position, and cooperated with upper limits and lower limits, which are arranged at edges on both sides of the frame; a receiving tray is arranged below the funnel, one end of the receiving tray is hinged to supporting legs of the receiving tray, and the other end of the receiving tray is cooperated with the funnel through a pulley mechanism. The alternate treating device disclosed by the invention has the advantages that the design is artful, the cost is low, the alternate treating device is easy to mount, the electric consumption is reduced, the cost is lowered, the efficiency is high, the service life is long, and problems are unlikely to occur.