Abstract: A crack was found in the inter stiffener of GH4110 high temperature alloy vent-pipe of starting engine when the plane was checked. Chemical compositions analysis, metallographic examination and fracture analysis were used to analyze the cracking reason of the vent-pipe. The results show that the grain boundary presented poor chromium in the pipe inwall surface because of the role of high-temperature gas erosion, which reduce the strength, lasting and fatigue properties of the alloy. The vent-pipe failure was the thermal fatigue cracking, which was caused by the stress concentration of the ground place, interior heat-stress and mechanical vibration.