The main material used in the cooling circulation water pipe for nuclear power is Q345, large diameter, thick plate, a plurality of weld seam, short space distance between reinforcement ring, and big constraint. Heat treatment shall be conducted as a whole in the furnace after the completion of welding operation in order to eliminate the stress. The heat treatment procedure is that the temperature of 600 ℃ shall be reached by heating and keep it for 2h then cool it in the furnace naturally .