Abstract: The Bauschinger effect of X80/X100 pipeline steels produced with a Steckel mill was investigated using uniaxial compression-tensile experiments under different deformation conditions.The results show that the absolute value of Bauschinger effect increases with the increment of pre-compressed deformation,and reaches saturation for X100 pipeline steel when the pre-compression is 1.5%.As the strength of the pipeline steels increases,the Bauschinger effect becomes more obvious.Under the experimental conditions,X80 and X100 pipeline steels represent transient softening and permanent softening,respectively.In combination with the chemical composition and the microstructural characteristics of X80/X100 pipeline steels,it is revealed that for the pipeline steels,the strength difference between soft and hard phases (M/A islands for instance),the volume fraction of hard phases,and the dislocation density in original microstructure are the key factors of Bauschinger effect.