Pipeline steel belongs to energy steel, which involves safety service and strict quality requirements. The mechanism of edge cracks in pipeline steel during hot rolling was analyzed from macroscopic characteristics and microscopic morphology. The analysis showed that the causes of edge cracks were related to slab width reduction and surface temperature difference. By using the vertical roll to reduce the width, the reduction was less than 30 mm; or by using the sizing machine to reduce the width, the reduction was more than 150 mm. The occurrence rate of defects was obviously reduced, which reduced the edge crack defect of X80 pipeline steel from about 15% to less than 4%, effectively improved the market share and customer satisfaction, and created good economic and social benefits for enterprises.