The invention belongs to the technical field of logistics storage, and particularly relates to an express storage cabinet for automatically fitting package size. The express storage cabinet comprisesa cabinet body, a storage module, a fetching module, storage boxes, a conveying belt, a flexible rod and a controller; the storage module is installed at one side of the cabinet body, and the fetchingmodule is installed at the other side of the cabinet body and correspondingly provided with a storage window and a fetching window; the middle part of the cabinet body is provided with a group of storage boxes, each storage box comprises a box body, a clapboard, a guide pillar, a driving block and a slide rail; both sides of the clapboard are provided with buffer air sacs, and the inner parts ofthe buffer air sacs are provided with pressure sensors. Through the buffer air sacs, the extrusion of the express package is reduced; the lower parts of the storage boxes are provided with conveying belts; the flexible rod is arranged in the inner part of the cabinet body, the flexible rod is used for moving the articles conveyed by the conveying belt in or out of the storage boxes; the controlleris used for controlling every module. Specific to different sizes of express packages, the size of the storage cabinet can be automatically stored, thereby realizing the high-efficient use of the storage space.