Abstract: For lost and stolen USB disk, put forward combining the hidden partition and data encryption protection method, using USB composite (USB composite device) structure model, established a hidden encrypted partition and a regular partition, when USB disk into the computer the ordinary partitions can be for users to use; the use of PC software and USB dynamic identity authentication, the authentication is successful can be dynamic mount hidden partition, the hidden partition data is filtered through the PC driver program encryption and decryption. After the actual test, security USB disk operation using simple, confidentiality good, fast speed of encryption and decryption, practical and effective, to achieve the expected goal.