Owing to small package,large capability and convenience,the mobile memory mediums are widely used. But they will lose secrets if lack of effective management in secret departments. Based on these considerations,we design a system for monitoring mobile memory mediums relating to secrets. This system is composed of a server and a device,the former is a popular computer and the latter contains an ARM board,a card reader and an annunciator.The system is cheap and simply constructed and will monitor the mobile memory mediums effectively to reduce losing secrets.