In this paper, the microstructure and corrosion behavior of a 1.0 wt.% Gd duplex stainless steel annealed at different temperatures were studied. Electron microscopy revealed that the content of secondary Gd-containing phase was increased along with the increasing annealing temperatures and then decreased at 1080℃ as an inflection point. A dual-phases M-Gd intermetallic with M3Gd as the core phase and M12Gd as the shell was the main type of secondary phase in the sample annealed at 1080℃. In the sample annealed at 1140℃, M3Gd phase was dominant. The corrosion behaviors of the two annealed steel samples were analyzed in NaCl, HCl and H3BO3 solutions. It showed that the sample annealed at 1140℃ had lower corrosion rate. M3Gd was more electrochemically active than M12Gd when the sample was immersed in NaCl and HCl solutions but more noble in H3BO3 solution.