The utility model discloses a hydrogen chloride synthesizer sight glass key belt cleaning device, include from last to being the high -position water groove down in proper order, the wash line, the automatic control switch valve, washing switch, the sprayer, wash the water knockout drum, the sight glass, press sight glass flange and sealed the pad, the furnace body connected nipple joint, open when a washing switch key, the automatic control switch valve is opened, the wash line is followed to high -position water inslot hot water, the valve, the sprayer, article three, branch road, it washesthe sight glass to rinse the water knockout drum, it finishes to wash can close washing switch, the above -mentioned convenient operation that makes, can wash in real time, do benefit to safe operation and safety in production, could carry out abluent problem to the sight glass when still having solved necessary blowing out or maintenance, lowers labor intensity, production processes has been optimized, the utility model discloses a key belt cleaning device that can extensively be arranged in the supporting sight glass of different work condition production.