The invention provides a miniature bridge-type structure and a preparation method thereof. The miniature bridge-type structure comprises four cantilever beams, a metal bridge floor, four metal piers and a substrate. Each cantilever beam is of an L-shaped structure, one ends of the cantilever beams are fixedly connected with the metal piers in a perpendicular mode, and the other ends of the cantilever beams are connected with the metal bridge floor; the metal bridge floor and the cantilever beams are located in the same plane, the metal bridge floor is hung on the substrate through the four cantilever beams, and a cavity structure is formed between the lower bottom face of the metal bridge floor and the substrate. The method induces the steps of preparing the metal piers on the clean substrate surface, coating the substrate surface where the metal piers are formed with a sacrificial layer, carrying out photoetching treatment on the sacrificial layer, then removing the portions, on the tops of the metal piers, of the sacrificial layer to expose the tops of the metal piers, carrying out solidified treatment on the sacrificial layer, preparing the metal bridge floor on the solidified sacrificial layer, removing the portion, at the bottom of the metal bridge floor, of the sacrificial layer to form a cavity, and building the bridge-type structure. The miniature bridge-type structure is large in tuning range and good in bridge floor parallelism.