The invention discloses a variable-cavity type sitting-preventing storage bucket for a shared bicycle. The variable-cavity type sitting-preventing storage bucket comprises a storage bucket body and anextending bucket body. One end of the extending bucket body is located in the storage bucket body, and the other end of the extending bucket body extends to the position below the storage bucket body. The two sides of each end of the extending bucket body are fixedly connected with one end of a first guiding rod, and the other end of each first guiding rod is fixedly connected with the lower sideof one end of a linkage flat plate. The other end of each linkage flat plate is embedded into a T-shaped sliding groove, the upper side of one end of each linkage flat plate is fixedly connected withone end of a second guiding rod, and the other end of each second guiding rod extends to be located above the storage bucket body and is connected with one side of the lower end of an inclined coverplate in an attached mode. The inclined cover plates enable the opening in the upper end of the storage bucket body to be of an inclined structure, and people cannot sit on the storage bucket; and ifa person insists to sit on the inclined cover plates, strong discomfortableness is generated, the purpose of sitting prevention is achieved, and the service life of the shared bicycle is guaranteed.