Abstract: Post-elevated temperature mechanical properties of butt-welded connections were investigated in this study. 39 specimens were heated to different maximum temperature from 200 to 800℃ and held for 60 minutes. They were subsequently cooled to ambient temperature naturally or by water, and finally stretched to failure. Results show that for butt-welded connections that fail in basic metal at room temperature, fracture failure happens, and the failure position changes to the butt weld when the exposed temperature is high. Cooling methods have a great effect on mechanical properties of butt-welded connections after fire when the exposed temperature is above 400℃. For natural cooling, specimens begin to fail in butt weld at a temperature of 500℃, and the maximum decreases in the ultimate strength and the corresponding deformation are 20% and 50%, respectively. For water cooling, specimens begin to fail in butt weld from 600℃, and the maximum decreases in the ultimate strength and deformation are about 10% and 35%, respectively.