Recently the U-Healthcare system has been rapidly advanced to manage emergence rescue for seniors. We can access emergency rescue systems with high quality services anytime, anywhere under ubiquitous healthcare systems. The more the various systems develop, the more software security systems become important. Therefore, the safety-critical system has been widely spread to the world by advancement of the information and communication technologies. There are a lot kind of fault analysis methods to evaluate software security systems. However due to characteristics of software that is not applied by human error, it can be prevented the enormous damages and losses from improving the safety of safety-critical system. So this paper proposes an integration method of FTA and Forward and Backward FMECA. This method has each strength of FTA and FMECA which is visual and numeric in normalization. First, by use of FTA, we can redraw FTA with Forward FMECA and Backward FMECA in consideration of occurrence, severity, detection, correctness, robustness, and security. Also according to value of NRVP at each event, we can modify FTA diagrams as shown critical paths given by severity and occurrence. Also, we propose the improved emergency rescue service platform of ubiquitous healthcare systems through identifying priorities of the criticality according to normalized risk priority values (NRPV).