The utility model discloses a well washing liquid storage tank with three-level filtering for downhole operation, and is applied to well washing liquid for oilfield well-repairing construction. A liquid storage tank is a rectangular tank which is welded by steel plates; an inner end part of a well washing liquid inlet is connected with a strong magnet scrap filter; a baffle plate is welded transversely in the liquid storage tank; the liquid storage tank is divided into a liquid storage chamber and a settlement filtering chamber by the baffle plate; a round hole is formed in the middle of the baffle plate; a partition plate is transversely welded in the settlement filtering chamber; a weir plate is transversely welded in the settlement filtering chamber; a filtering screen is transversely fixed in the settlement filtering chamber; and a well washing liquid outlet is welded on the lower part of the other end of the liquid storage tank. The well washing liquid storage tank has the effects that iron particles are collected by the strong magnet scrap filter; the flowing direction of the liquid is changed by the partition plate and the weir plate to reduce the flow velocity and settle the impurities contained in the liquid; the filtering screen is further used for filtering, and the cleaning well washing liquid flows out through the outlet so as to reduce the contents of the impurities in the well washing liquid.