The utility model discloses a filtering device for a finished diluent. The device comprises a diluent finished product tank, a self-priming pump, a double-cylinder filter and a straight-cylinder filter, a discharge hole is formed in the bottom of the diluent finished product tank; the discharge port is connected with the input end of the self-priming pump through a discharge pipe; the output end of the self-priming pump is connected with the inlet of the double-cylinder filter; the double-cylinder filter comprises a filter A and a filter B; slag discharging openings are formed in the bottoms of the filter A and the filter B; filter elements are arranged in the filter A and the filter B, filter bags are arranged on the filter elements in a sleeving mode, an outlet of the double-cylinder filter is connected with a bottom feeding port of the straight-cylinder filter through a double-cylinder filter discharging pipe, and a straight-cylinder filter discharging port and a straight-cylinder filter slag discharging port are further formed in the bottom of the straight-cylinder filter. The double-cylinder filter is simple in structure, large impurities and fine impurities are effectively filtered together by connecting the double-cylinder filter and the straight-cylinder filter in series, and the filter bag is easy to replace, low in price and low in cost.