The invention discloses a dielectric geometric phase metasurface structure material with a low depth-to-width ratio and a structural optimization method thereof. The dielectric geometric phase metasurface structure material comprises a substrate, a reflecting layer on the substrate, a multi-beam interference layer on the reflecting layer and a dielectric nano brick array formed by periodically arranging a plurality of dielectric nano bricks with consistent sizes on the multi-beam interference layer, wherein the dielectric nano brick array is used for receiving perpendicularly incident circularly polarized light and adjusting the phase of the emergent light through adjusting the direction of each dielectric nano brick. The depth-to-width ratio of the dielectric geometric phase metasurface structure material is reduced to half of the depth-to-width ratio of the traditional transmission-type metasurface material, and the depth-to-width ratio is about 1.7, so that the requirements for theprocessing technology are reduced, and the finished product rate and mass production of the device are guaranteed.