Abstract: For evaluating the image quality of X-ray security inspection system objectively, according to the testing methods and requirements about image quality evaluating of standard GB 15208—2005, referring to the process of subjective evaluation, the image processing and mode recognition methods were put forward. ROI-based feature extraction method was carried out for testing block A, while color information based feature extraction method was carried out for testing block B. The principles, processes and key steps of the two signal processing methods were introduced, and thus software system was designed and achieved. Testing results showed that the recommended algorithm was high in accuracy even while the images being of noise and distortions, so it could evaluate the image quality objectively according to the standard.