Based on the tri-satellite positioning theory of generalized RDSS system SAR service, the paper analyzes the key performance characters of service area, positioning accuracy, position report time and SAR information link of generalized RDSS system SAR service. Simulation results show that generalized RDSS system SAR can provide the service with the most position report performance at global service area, quick positioning, in-time position report, reliable SAR information link, independent position ability and safe information transform.