Based on the comprehensive processing and the alarm calculation of multiple navigation information, Ground Proximity Warning System is of great significance for avoiding controlled flight into terrain accidents and improving aircraft safety. First，the paper introduces the working principle of Ground Proximity Warning System, and studies the design technology of the alert envelope based on the SOC curve. Second, as an example, the warning mode of the high near ground rate is taking to simulate the alerting envelope. Finally, by using the actual fighting data, the rationality of alerting envelope and the reliability of navigation information are analyzed to affect the performance of the system.