The fatigue crack propagation behavior of DD6 nickel-based single-crystal superalloy was investigated at temperatures ranging from 530 °C to 850 °C. The fatigue properties were assessed along the [001] direction, parallel to the loading axis in tension. After the fatigue crack propagation test, the fracture morphology was examined by scanning electron microscope and classified into four zones, including source zone, prefabricated crack zone, stable extension zone, and rapid extension zone. Electron backscatter diffraction was utilized to observe the profiles of plastic deformation perpendicular to the fracture. Additionally, the dislocation motion mechanism near the fracture was studied by transmission electron microscope. Results show that oxidation occurs at 650 °C under combined influences of the temperature field, stress field, and exposure time. Furthermore, due to weakened γ′ phase, a significant number of consecutive dislocations form in the γ and γ′ phases between 650 and 760 °C, resulting in increased oxidation of alloy. Besides, a notable decrease in fatigue propagation life can be observed at 760 °C.