The invention discloses a Web application safety situation assessment system based on multi-source data fusion. The system comprises a vulnerability information acquisition subsystem, a Web application ecological environment detection subsystem, a Web application safety situation assessment subsystem and a safety situation display subsystem. The system achieves the technical effects that the system is capable of finishing vulnerability scanning efficiently and accurately, the cases of vulnerability false alarm information and unavailable detection are reduced, the timeliness and the expansibility of a vulnerability scanning system are relatively good, and the presentation mode is reasonable.