Abstract: A new building weathering steel was treated at solution treatment temperatures of 1 025-1 200 ℃. The effects of solution treatment temperature on the microstructure, mechanical properties and corrosion resistance of the new building weathering steel were studied by observation of micro morphology, mechamical property testing and electrochemical testing. The results show that ferrite and austenite were the microstructure for both hot-rolled weathering steel and solution-treated weathering steel. when the solution treatment temperature was 1 175 ℃, the ratio of ferrite content and austenite content in the weathering steel was close to 1∶1. The strength and Rockwell hardness of the solution-treated weathering steel were lower, but the percentage elongation after fracture, percentage reduction of area and impact absorbed energy were higher, comparing with the hot-rolled weathering steel. At solution treatment temperature of 1 175 ℃, the weathering steel had high strength and hardness, and got the maximum values in toughness, plasticity and impact absorbed energy. The polarization curves and electrochemical impedance spectroscopy results show that the weathering steel had the best corrosion resistance when the solution temperature was 1 175 ℃.