The invention discloses a fully automatic warehouse storage device and a working method thereof, comprising a storage cabinet, the storage cabinet includes a housing, a plurality of partitions are fixedly installed inside the housing, and a plurality of pick-and-place panels are provided on the front side wall of the housing. Each partition is located under each pick-and-release port, and a belt conveyor A is installed on each partition, and a guide mechanism is installed on the front side wall of the housing. A sliding platform is installed on the guide mechanism, and a sliding platform is installed on the sliding platform. Belt conveyor B, a lifting mechanism is also installed on the storage cabinet, the lifting mechanism is connected with the sliding platform, the lifting mechanism drives the sliding platform to move up and down along the guide mechanism, and a control mechanism is also installed in the storage cabinet, and each belt conveyor A is connected to the sliding platform. The regulating mechanism is connected, and the regulating mechanism controls the operation of each belt conveyor A; the purpose of the present invention is to solve the problem of limited shelf height, waste of use space, excessive labor intensity, and manual climbing caused by manual picking and placing of articles. There are problems such as danger.