Abstract: Analysis of the Stem-fillet blend fracture of exhaust valve was conducted by means of macroexamination,microstructure examination,chemical composition analysis and hardness test. The results indicated that the fracture mode is the fatigue failure. According to the unload through its working. It is believed the valve failure is because the valve stem to guide clearance is excessive,and that causes the high seating speed that impacts the valve,so the fatigue source occurs in the valve fillet after a long time. The impact of valve tip from the rocker arm increased,at the end the valve stem-fillet blend cracked.