The invention relates to the field of manufacturing of an RF MEMS device, and discloses a preparation method of double-layer optical resist sacrificial layers of an RF MEMS device. The preparation method mainly comprises the four process steps of preparation of a first sacrificial layer by negative glue, curing of the first sacrificial layer, preparation of a second sacrificial layer by positive glue and curing of the second sacrificial layer; wherein during the preparation process of the second sacrificial layer, the preparation of the sacrificial layer with contact suspension structure is realized by exposing with a mask with photo-etching holes. With double-layer optical resist as sacrificial layers, the preparation process is simple, the flattening effect is good, the release is easy, and the sacrificial layer with contact suspension structure can be prepared conveniently.