Abstract: A series of heat treatment tests are conducted to the X100 seamless steel linepipe via different quenching and tempering processes in a bid to study the influence by quenching and tempering temperatures on the microstructure and properties thereof.The test results show that the said pipe can be fully austenitized，and both the acicular ferrite and lath bainite structures can be obtained as well when the quenching temperatures reaches at 930℃and above.Along with the change of the tempering temperature，the microstructure and properties of the X100 steel pipe as tested present certain regularities.After quenched at 930℃and tempered at 620℃，acicular ferrites as in fine grains and uniformly distributed are obtained in the tested pipe，and the pipe also has the best comprehensive performance.