The invention discloses a wet etching technology for an MEMS device. The wet etching technology comprises the following steps that a substrate is etched to form a groove, and the groove is passivated with plasma gas to form a polymer passivation layer on the surface of the groove; the passivation layer on the bottom surface of the groove is removed, and the lower surface of the silicon substrate is subjected to mechanical polishing to form a mechanical damage layer; the mechanical damage layer is removed with a silicon etching solution, and photoresist is removed; a sacrificial layer is removed, wherein large-scale transverse drill etching is conducted with a wet etchant, the independent part not needing to rely on a support is retained, and the sacrificial layer is selectively removed; and substrate removing and thinning are conducted, wherein uniform substrate removing and thinning are implemented according to a physical grinding mechanism with a chemical etchant to quickly remove materials on the front face or back face of a wafer. The wet etching technology is easy to operate, low in cost and high in efficiency, and the etching pattern obtained when the MEMS sacrificial layer is made through wet etching can be flexibly controlled.