Recent years people have witnessed a surge of interest in APT attack, due to its complexity and persistent attack characteristics. In this paper, we give an overview of APT attack and attack graph and also use attack graph to assist in predicting the APT attacks and identifying the most vulnerable resources. In order to prevent APT attacks, this article improves the attribute attack graph by depending on the APT attack stage model and puts forward the stage attribute attack graph. Experimental results showed that the stage attribute attack graph can accurately reflect the lifecycle of attacks, meanwhile identify the most vulnerable resources and predict the APT attacks to defend APT attacks on each APT attack stage in time.