A security system and a security method of stored data are provided. In the security system and the security method, a central processing unit performs hashing operation on a seed code to generate a data access code, which is then compared with a password stored in a storage device. If there is no password in the storage device, the data access code is written into the storage device as the password. On the other hand, if the data access code does not match the password, the storage device denies the access request from the central processing unit.