With the increase of the proportion of hot delivery and hot charging in pipeline steel continuous casting slab， the cut continuous casting slab are prone to quality defects due to the coupling effect of phase transformation， thermal stress， and temperature， resulting in huge economic losses.This article takes X70 pipeline steel as the research object，by comprehensively considering the nonlinear changes of material thermal properties parameters with temperature and the setting of boundary conditions， the ABAQUS finite element analysis software is used to conduct thermal coupling numerical simulation analysis on the cooling process of X70 pipeline steel 4 500 mm × 2 300 mm × 300 mm continuous casting slab. The conclusion shows that the average heat dissipation rate of the center of gravity of the slab is 0.076 ℃/s， the surface center is 0.084 ℃/s， and the temperature difference between the surface and the center is between 100 ℃ and 210 ℃， which gradually decreases over time. The stress value at the edge of the slab is 25 MPa， and the thermal stress within 300 mm of the edge is roughly the same， within 200 MPa. Considering the changes in temperature field， the cutting time to the heating furnace should be shortened as much as possible， or insulation measures should be added to prevent quality defects caused by excessive thermal stress.