Abstract: “TIG cold welding+UNGW” combined welding process was employed to fabricate 1Cr17/1Cr18Ni9Ti dissimilar steel joints. Subsequently, these joints underwent aging treatment at 200 ℃ and 350 ℃ for 144 hours respectively to simulate their long-term service process at high temperatures below 400 ℃. The microstructure of different zones in the combined welded joint was examined using optical microscopy and scanning electron microscopy, while the effect of aging temperature on the corrosion resistance of the joint was investigated through electrochemical tests and intergranular corrosion tests. The results show that no significant microstructural changes were observed in different regions of the combined welded joint after aging treatment at 200 ℃×144 h and 350 ℃×144 h compared with those in the as-welded state. The corrosion tendency of the combined welding joint did not show remarkable increase with the rise of aging temperature. However, the corrosion rate demonstrated a growing trend with increasing aging temperature, though the change was not significant.