Abstract: The fracture features of single crystal superalloy DD6 were investigated under the condition of low-cycle fatigue(980 ℃, 760 ℃)and fatigue-creep. The results show that the low-cycle fatigue fracture surface had more than one source zone and the fatigue cracks initiated at surface or subsurface of the specimens. The fatigue cracks propagated along the crystallographic plane first and then perpendicularly to the loading axis. Typical fatigue striations and river pattern formed in the steady propagation stage. Like-cleavage steps were observed at the fast fracture zone. The fracture surface forming in the initial stage is perpendicular to the principal stress axis, and then the cracks propagated along the direction 45 degree away from the principal stress axis. Compared with the fracture surfaces of the low-cycle fatigue specimens tested under the same condition, those of the fatigue-creep specimens have the following distinct features: more serious oxidation and smaller extension zone.