The utility model relates to the technical field of vacuum coating equipment, in particular to a device for protecting an observation window of vacuum coating equipment. The device comprises a cylinder formed by rolling a thin stainless steel plate, a fixed stop piece and protection glass. According to the device disclosed by the utility model, the protection glass can be clamped in an inner cavity of an observation window seat and is attached to observation glass so as to achieve an optimal observation effect; a gap is formed between the observation glass and a vacuum cavity and is positioned on the protection glass, so that pollutants can be stopped; the pollutants are effectively prevented from being deposited on the observation glass, the detaching frequency of the observation glass is reduced, the observation glass is prevented from being polluted, and the aim of protecting the observation window is fulfilled. The device is manufactured from the thin stainless steel plate with the fixed stop piece, so that the complicated processing is not needed, and the device is easy to manufacture. When the protection glass becomes obscure after being used for a long time, only the cylinder is taken out of the inner cavity of the observation window seat and then is unfolded, so that the protection glass can be taken down for cleaning, and the device is convenient and easy.