The invention relates to an impact water film deductor and the application thereof in a vacuum suction system in sodium benzoate production. A reverse-suction preventing device capable of containing one quarter of dedusting water is arranged between the impact water film dedustor and a waste gas inlet; an exhaust port is arranged on the upper part of the dedustor opposite to an air inlet; an airflow increasing device is arranged under the dedusting water in the deduster; a 2 to 4 level baffle plate is arranged between the dedusting water surface and the exhaust port; a dedusting water inlet and a communicating vessel for observing the liquid level are arranged outside the dedustor; in the production of sodium benzoate, a vacuum pipeline of the vacuum suction system is connected with the waste gas inlet of the reverse-suction preventing device of the impact water film dedustor from the upper part of a mater storing chamber; the exhaust port of the impact water film dedustor is connected with a vacuum pump; and the dedusting water is distilled water and can be reused in sodium benzoate production. In the invention, the material suction process flow of original granular sodium benzoate production is changed, ultrafine dust of sodium benzoate in vacuum pumping tail gas is completely removed, and the sodium benzoate is recycled.