Aiming at the special requriement of the mobile hing-capacity storage device's safety in the special field, based on SSX20-D security chip, we designed the security model with three levels: data storage security protection, usb flash disk key parameter protection and usb flash disk using management. The security chip uses many security mechanisms, including data encryption, usb flash disk parameter protection, encryption key protection, password-hardware using control, and the usb flash disk anti-attack ability. The mechanism expended the Key's safety to the hing-capacity storage chip. Especially it designed three-level key-protection method which can solve the safety weakness of the key parameter protection. We are using SM1, SHA-256 and self-defined function to make sure absolute security of the key.