The invention discloses a processing method based on secondary wet etching. The method comprises steps that S1, after primary etching, a wafer after primary etching is processed through employing a baking mode to enhance adhesion between optical cement and the wafer; S2, a reaction ion beam method is employed to process a surface of the wafer, a high-molecule polymer layer is formed on the surface of the optical cement; S3, particles formed during primary etching are removed through employing ammoniacal liquor having certain concentration; and S4, secondary etching is carried out. The method is advantaged in that before secondary etching is carried out, the optical cement baking process is further added, an F-based gas optical cement processing mode containing C is combined, surface adhesion is enhanced, the polymer layer is formed on the surface, surface processing is carried out through employing a weak aqueous alkali such as the ammoniacal liquor to remove the surface particles; on the condition that etching depth is precisely controlled, etching quality is further improved, and excellent performance of a compound semiconductor device is guaranteed.