A MEMS phase shifter, including: a substrate; a coplanar waveguide signal structure on the substrate; two coplanar waveguide ground wires respectively at two sides of the coplanar waveguide signal structure; insulating isolation layers respectively on the two coplanar waveguide ground wires; and a metal film bridge across and over the coplanar waveguide signal structure and forming a gap with the coplanar waveguide signal structure, both ends of the metal film bridge respectively attached to the insulating isolation layers on the two coplanar waveguide ground wires, wherein an insulating dielectric layer is provided on the coplanar waveguide signal structure, and the insulating dielectric layer comprises at least one concave part, which is concave in the direction towards the substrate, on the surface facing the metal film bridge.