Abstract: Cyberspace security situational awareness is devoted to relfecting the dynamic cyberspace security environment from an overall point of view, and makes the evaluation and analysis of the trend of the cyberspace security. As a new hotspot in the field of cyberspace security, academic research on cyberspace security situation awareness has made numerous achievements, but the construction and application of such system is rare. In this paper, the basic concept of cyberspace security situation awareness is introducd, the functional requirements, architecture and key technologies of cyberspace security situational awareness system are described, two typical application situation analysis, i.e. vulnerability and security situational analysis&evaluation, are illustrated in detailed .