The evolution of microstructures and mechanical properties stimulated by long-term service was investigated using a GTD111 blade employed in the first stage rotor blade of a heavy-duty gas turbine. Results show that the microstructures of the blade are mainly composed of γ matrix, γ′ precipitates with two dimensions, γ+γ′ eutectic and MC-type carbides. The microstructural degradation of the blade is closely related to its structural characteristics. Samples from leading edge and middle region of the blade exhibit a relatively lower degree of microstructural degradation, while samples from trailing edge of the blade possess higher degree of microstructural degradation. The ultimate tensile strength (UTS) of the leading edge region is significantly higher than that of the trailing edge region at room temperature, but the UTS of different regions has little difference at 982 °C, which may be related to different deformation mechanisms at higher temperatures.