A semiconductor memory device includes a controller module as well as a universal interface module and a semiconductor memory medium module, which are connected electrically with the controller module respectively. The device also includes a one-time programmable memory, which stores a unique serial number. This one-time programmable memory is provided within the controller module or the semiconductor memory medium module. The number sequence of the unique serial number contained in each of the semiconductor memory device is different from that of another semiconductor memory device. While providing a mobile data storage function, this invention adopts a security technology to prevent from illegal data reading/writing. This increases significantly the difficulty in decrypting the data of a legal user, subsequently improving the security of the stored data of the user greatly. This invention also provides a method for realizing secure data storage with this semiconductor memory device. With the help of the unique serial number in this semiconductor memory device, the user can protect the stored data. This invention can be extensively used in information security fields, including ID authentication, copyright protection, etc.