The invention discloses an anti-acid mist type battery filling cap. The battery filling cap comprises a cap body, wherein the cap body is sealed with a battery cap through threads; a labyrinth loop is arranged on the top surface of the cap body; a cap is arranged at the upper part of the cap body, and covers the labyrinth loop; an anti-acid mist piece is arranged in the cap; a reflowing hole is formed in the centre of the labyrinth loop; exhaust holes are formed in the cap. During the use of the storage battery, acid mist brought from the decomposed electrolyte solution passes through the labyrinth loop to form liquid drops to flow back into the storage battery, a small quantity of acid mist which does not form liquid drops is filtered through the anti-acid mist piece, and gas generated by water decomposition is exhausted through the exhaust holes in the cap. Therefore, the content of a combustible gas in the storage battery is reduced, the acid volume in the electrolyte solution of the storage battery can be efficiently guaranteed, and the service life of the storage battery is prolonged.