In order to investigate creep-fatigue life characteristics of Inconel 738LC, fatigue and creep-fatigue tests were carried out at 850℃. Significant life reduction to 30% to 50% of normal fatigue life, occurred when a strain hold period was introduced at the minimum compressive strain. Test results showed that the degree of life reduction did not depend on the length of hold time. To clarify the creep-fatigue damage mechanisms under creep-fatigue loading, in-situ SEM observations were carried out during the tests. In the tensile strain hold test, multi-site grain boundary cracking was observed from the beginning of the test. On the other hand, only a single main crack was observed in the compressive strain hold test. The crack propagated in an intergranular manner and it was different from the features observed under cyclic fatigue conditions. Through detailed observation, it was found that grain boundary sliding damage occured at most surface grain boundaries. In order to investigate creep-fatigue life characteristics of Inconel 738LC, fatigue and creep-fatigue tests were carried out at 850 ° C. Significant life reduction to 30% to 50% of normal fatigue life, occurred when a strain hold period was introduced at the Test results showed that the degree of life reduction did not depend on the length of hold time. To clarify the creep-fatigue damage mechanisms under creep-fatigue loading, in-situ SEM observations were carried out during the tests. In the tensile strain hold test, multi-site grain boundary cracking was observed from the beginning of the test. On the other hand, only a single main crack was observed in the compressive strain hold test. The crack propagated in an intergranular manner and it was different from the features observed under cyclic fatigue conditions. Through detailed observation, it was found that grain boundary sliding damage occured at most surface grain boundaries.