The invention discloses a large-capacity smart express item box capable of automatically accessing items. The large-capacity smart express item box includes a cabinet body and a mechanical hand disposed at the rear end of the cabinet body. The cabinet body is provided with an access window, the bottom of the access window is provided with a conveying belt, and the top of the access window is provided with a detection unit. The detection unit is used for detecting the size of an item. A bracket is disposed in the cabinet body, a plurality of columns of storage grids for storing items are arranged in the cabinet body, a sliding mechanism is arranged between a partition plate and the cabinet body, a driving mechanism drives the partition plate to slide along the sliding mechanism, and each storage grid is separated through a clamping groove. A telescopic mechanism is arranged in the access window and connected with a push plate. When the items are stored, after the sizes of the items aredetected, the mechanical hand captures trays on the bracket to the rear end of the conveying belt, the conveying belt conveys the items to the trays, the mechanical hand conveys the trays storing theitems to the storage grids, and the trays are placed in different clamping grooves. When the items are taken, the mechanical hand captures the trays into the access window, and after the items are taken, the mechanical hand places the trays back to the bracket. The express item box is high in space utilization rate and facilitates users' taking and storing the express items.