The invention discloses a deep silicon etching method, and relates to the technical field of semiconductors. The method can improve the morphology of a sidewall. The deep silicon etching method comprises an initial deep silicon etching stage, the initial deep silicon etching stage comprises a plurality of primary deposition steps and a plurality of primary etching steps, the plurality of primary deposition steps and the plurality of primary etching steps are alternately carried out, the deposition time duration of the plurality of primary deposition steps successively decreases, and the etching time duration of the plurality of primary etching steps successively increases. The method is used for deep silicon etching.