The invention discloses a portable information security device in the security field. In order to solve the problem that the USB Key transfers data at low speed and may occupy more CPU resources with USB master/slave protocol, and to meet the demand on development of the next generation of interface technology, the invention provides a portable security device, based on serial ATA protocol, comprising an eSATA interface unit, a memory unit, a privilege management unit, an algorithm unit and a control unit.