The invention discloses a method for cleaning a sizing agent corroding a silicon nitride mask. The method comprises the following steps: (1) ultrasonically cleaning the sizing agent in aqueous ammonia solution; (2) ultrasonically cleaning the sizing agent in pure water for at least two times; (3) ultrasonically cleaning the sizing agent in dilute hydrochloric acid solution; (4) spraying the pure water on the sizing agent; and (5) dipping the sizing agent in circulating pure water. The cleaning method of the invention can completely eliminate residual sizing agent and various impurities on the surface of a silicon chip and prevent incomplete cleaning of the residual sizing agent from causing a negative effect on the battery performance.