The creep deformation and rupture behavior of CLAM steel has been studied in this article.Creep test were carried out at 923K over a stress range of 90-140MPa.The microstructure of the deformation zone and the undeformed zone of the creep samples were characterized by scanning electron microscope(SEM)and transmission electron microscopy(TEM).The results showed that under different stress state,the ductile fracture under high stress is changed into brittle fracture under low stress.The relationship between minimum creep rate and applied stress followed Norton power law relation,and the stress exponent value n is 8 at 923K.The precipitates in the samples are obviously increased and grown up.Laves phase could be found in the deformation zone and the creep stress could promote the formation of Laves phase.