In this paper, the creep-fatigue behavior of a nickel-based superalloy GH720Li widely used for the turbine disk of an aero-engine was experimentally investigated. The cylindrical bars cut from an actual turbine disk were employed. The creep-fatigue tests with different dwell times were performed at 650°C. Experimental results revealed GH720Li is very sensitive to dwell time at 650°C, i.e., at the longer hold time (> 30min), the creep damage is dominant, thus decreases the creep-fatigue life. Then, the mechanism of creep-fatigue failure was discussed by using the SEM analyses of the fracture surface. It was found that with the increase of dwell time, the failure mode of the crack formation zone is transformed from a mixture of transgranular and intergranular to an intergranular failure. In addition, the crack formation zone is transformed from an intergranular fracture to a mixture failure mode. Finally, based on the experimental data, loading patterns transformation method and AMWD method were applied to predict the creep-fatigue life, and the applicability of two models was discussed.