Aiming at the difficulty in analysis of binary program vulnerabilities, an approach for software vulnerable spots localization based on taint analysis was proposed, and a corresponding tool named SwordChecker was implemented. This method is based on dynamic taint tracing. Software vulnerable spots were localized by character matching according to vulnerability patterns, and sensitive bytes which affected the vulnerable spots were localized by binary-search. Experiment results show that SwordChecker can accurately identify and localize three types of software vulnerable spots fast, has successfully analyzed the causes of multiple open vulnerabilities, and has assisted mining several undisclosed vulnerabilities.