Abstract: Investigated are the effects by different quenching and tempering temperatures on the microstructure and properties of the S135 drill pipe.The test results show that both the yield strength and the tensile strength of the pipe are decreased along with increasing of the tempering temperature, while in contrary its toughness and plasticity are going up.The quenching temperature just slightly affects the properties of the steel as tested.The tested steel shows good mechanical properties under the the conditions as quenching temperature:880℃, and holding time:30 min;tempering temperature:from 540℃to 580℃and holding time:60 min.