Abstract: The ferrite/pearlite banded structure as formed due to component segregation shall cause anisotropy of the mechanical properties of the high-strength pipeline steel.The effects by the ferrite/pearlite banded structure on the thermal deformation behavior of the X80 pipeline steel are investigated by means of the thermal deformation test.As a result it is identified that compared with the ferrite band,the pearlite band stays with obvious stress concentration;whereas the difference between the rolling directional thermal expansion coefficient and the transversal thermal expansion coefficient is so little,which means that although the banded structure affects the distribution of the micro-thermal deformation,it so slightly affects the thermal expansion coefficient of the high-strength,low alloy X80 steel.