Situational awareness plays a main role in the power security defense system. Aiming at the problem that the current power system situational awareness method cannot describe the safety distance quantitatively and the evolution speed of the future system, a trend analysis-based power system situational awareness method is proposed in this paper. Based on trend analysis , a novel situational awareness framework is proposed. On the basis of information acquisition, the N-1 static safety distance model is introduced to evaluate the security level of the current and future state of the system. By combining the safety distance model with qualitative trend analysis, the moving direction and trend change rate of the operating point in the future change state are automatically captured, so as to improve the ability of the system security situational awareness. The application results of IEE 118-bus system and actual power system show that the proposed method can effectively help system operators to monitor, predict and prevent potential problems.