Abstract: The behaviour of cyclic endurance failure have been researched under different conditions of temperature and hold time. Two kinds of heat treatment method are used to get the different structure of grain boundary. The results show that the alloy with both kinds of G.B. state are all not agreement with Linear - Damage Summation, t/tr +Nj/Nf = 1 under conditions of temperatuers 750, 800, 850, and 900℃, and hold time 0-32（min）. In general, all specimens are strengthened very clearly. There is great influence of hold time on the cyclic failure life of alloy. The peak of this life vs hold time is occurred. Trend of weakening is begun when hold time is shorter than 3 min.The micro - mechanism have been analyzed by means of TEM, SEM and "so" on. These phenomenon are explained with dislocation structures and anela-sticity.