Abstract: The tensile tests of P280GH steel elbows used in nuclear power plant were carried out at different temperatures (25,50,100,150,200,250,300,316℃) under heat treatment for mechanical properties (HTMP) condition, heat treatment for mechanical properties and simulated stress relieving heat treatment (HTMP+SSRHT) condition. The effects of temperatures on the tensile properties of P280GH steel elbows with different heat treatment conditions were studied. The results show that the tensile strength and yield strength of P280GH steel elbows in HTMP state were higher than those in HTMP+SSRHT state. In the two states, when the temperature rose from room temperature to 316℃, the tensile strength of P280GH steel first decreased and then increased, and the yield strength continued to decrease, and the "blue brittleness" phenomenon appeared at 300℃. When the service temperature was 150~250℃, the mechanical properties of the material should be tested under the service temperature.