The reliability endurance test is an important method of increasing and ameliorating equipment reliability. Using the method of accelerated test to assess reliability life span is a positive aspect at present. In view of the reliability fatigue life of the aircraft auxiliary fuel tank cone, this paper adopts the method of accelerated test to assess its life span. The result shows that the combination method of the accelerated test in workshop and the test-flight in airfield is an effective way of determining equipment reliability life span.