Disclosed are an entangled state preparation method and device based on a superconducting quantum bit and a Rydberg atom. With the help of two strong microwave driving fields, an unconventional geometric quantum gate is achieved, as to complete the preparation of a maximum entangled state. The influence of a laser field and a magnetic field required by the Rydberg atom and a radiation-cooled superconducting coaxial cable on the coherence of the superconducting quantum bit may be reduced.