The invention discloses a device for washing phosphoric acid tail gas and cogenerating sodium fluosilicate. The device comprises a venturi tube, a washer liquid tank, a washing tower I, a washing tower II, a tail gas washer, a defoamer, a tail gas fan, a tail gas chimney, a washer liquid geosyncline, a venturi tube washing pump, a filter press feed pump, a frame filter press, a fluosilicic acid pool, a fluosilicic acid pump and a sodium fluosilicate reaction tank. The invention also discloses a process for washing phosphoric acid tail gas and cogenerating sodium fluosilicate. The process comprises the following steps: washing the phosphoric acid tail gas with water, wherein the fluosilicic acid is dissolved in water; adding sodium sulfate into the water with the dissolved fluosilicic acid for reaction to generate sodium fluosilicate and sulfuric acid; and filtering to obtain sodium fluosilicate. The invention solves the problem of using the byproduct fluosilicic acid in the production process, improves the operation quality of the environmental protection equipment in plants, guarantees the environment quality and creates new economic growth points.