The invention relates to a security threat analyzing method based on a service data stream model. The method includes the steps of establishing the service data stream model, decomposing an information system, analyzing key service flow, recognizing and grading sensitive data, and analyzing the security threat. According to the technical scheme, by establishing the key service data flow link of the information system on the basis of the service data stream model, introducing the security grades of the sensitive data, and recognizing the security threat of each key service flow and conducting formal representation according to the key service data flow model, a user can be helped to design the security threat analysis better conforming to the system service flow, and therefore the overall security of an application system is enhanced.