Abstract: The simulation test of the heat affected area of X60 steel for linepipe is made by means of the welding thermal simulation technique. The toughness and structures of the said steel at different peak temperatures and with different cooling times are studied, and the hardness of its heat affected area measured. The result demonstrated that the higher the peak temperature, the coarser the structure of the steel, and the lower its toughness, and that the influence by the cooling time on the structure and toughness of the steel's welding heat affected area varies with different peak temperatures.