Abstract: To investigate the high-temperature service safety of TP347H FG pipe material, a study was conducted on the microstructure, corrosion products, and mechanical properties of TP347H FG pipe material exposed to a thermal environment of a 600 ℃ ultra-supercritical thermal power unit for 50 000 hours. A comprehensive analysis was conducted on the grain size of the inner and outer walls of the workpiece, the corrosion mechanism, and the tensile properties after service, using metallographic microscopy, X-ray diffraction, scanning electron microscopy, and energy-dispersive spectroscopy analysis. Results show that the surface of the service-exposed workpiece shows a reduction in the thickness of the grain refinement layer, compared to the as-received workpiece. Both the fire-facing side and the non-fire-facing side oxidation layers exhibit a double-layer structure, which effectively enhances the corrosion resistance of the material in high-temperature flue gas environment. Due to the precipitation of fine intragranular phases of both the fire-facing side and the non-fire-facing side, the yield limit is improved compared to the as-received pipe material. However, the precipitation phases weaken the role of the grain boundaries, resulting in a significant reduction in the elongation of the workpiece and the emergence of local brittle fracture.