Abstract: During shear process, lamellar cracking appeared on the shear section of 700 MPa grade hot-rolled high strength steel plate. The causes of lamellar cracking were analyzed by means of morphology and microstructure observation, chemical composition analysis,micro area composition analysis and tensile property testing. The results show that the serious ferrite-pearlite banded structure caused by composition segregation in the high strength steel was the direct cause of lamellar cracking, and the growth of small holes near the large-sized second phase particles or inclusions in the deformation area at crack tip aggravated the crack growth. By controlling the starting speed and stable casting speed of the continuous caster, adjusting the precision of the roller gap in the sector section, and taking various measures to improve the purity of liquid steel, there was no lamellar cracking in the high strength steel during shear process.