In these years, many researchers proposed the way — to isolate the computers with sensitive information from outside attackers or unauthorized users. The Taiwan government has ruled the importance of network isolation in several policies, such as “The Handling Implementation Program of Information Security Emergency Incidents for government departments” and “The Responding Protocol of Notifying Information Security Events in Executive Yuan and its Departments.” However, there are few materials available for implementing network isolation. In ISO-17799, there is no implementation guidance for practicing network isolation but auditing network physical isolation. This paper provides the implementation guidance of network isolation with some logical isolation techniques and management polices.