The utility model discloses a passive washing and filtering system for airborne radioactive effluent of an underground nuclear power plant. The passive washing and filtering system comprises a metal tank which is arranged in an underground cavern and is filled with a certain amount of filter iodine solution; a gas inlet tube which is communicated with a safety shell is arranged below the side wall of the metal tank and is communicated with a plurality of branch tubes in the metal tank; Venturi tubes are densely distributed on each branch tube; the top of each Venturi tube is lower than the liquid level of the filter iodine solution; a gas outlet tube which is communicated with a chimney is arranged on the top of the metal tank; a metal fiber filter is arranged below the gas outlet tube; a heat exchange tube is arranged between the Venturi tubes and the inner wall of the metal tank; the heat exchange tube is communicated with a cooling water pool on the ground; a liquid injection tube and a liquid discharging tube are also arranged on the side wall of the metal tank. The utility model provides the washing and filtering system which is passive and capable of regulating pressure relief automatically, can be operated effectively for a long time and can be used repeatedly by combining the characteristics of the underground nuclear power plant and a working principle of the Venturi tubes.