The invention discloses a defoaming device of a plate type falling film evaporator capable of enhancing vapor-liquid separation level and improving defoaming effect by rapidly reducing high-speed vapor streams. The defoaming device comprises an outer protective frame and a plurality of mutually parallel baffle plate damping vanes, wherein the plurality of mutually parallel baffle plate damping vanes are arranged in the outer protective frame; defoaming channels are formed among the baffle plate damping vanes; each baffle plate damping vane is bent into an inlet section, an outlet section and a bent section positioned between the inlet section and the outlet section and formed by bending the baffle plate damping vane for a plurality of times; and an exterior angle of the corner of the bentsection is provided with an L-shaped fin used for obstructing the flow direction of steam. The invention has the advantages of being capable of rapidly reducing the vapor streams, obviously improvingthe defoaming effect, enhancing the defoaming efficiency and quality, preventing the effective components contained in secondary steam from being brought out and reducing the production cost.