Abstract: It is of great significance to carry out the cause analysis of black spots and warping defects of SAE1022 boron-containing steel surface for improving the quality and production stability of its hot-rolled plates. The microstructure morphology and composition analysis of the black spots and warping defects on the hot-rolled plate surface of SAE1022 boron-containing steel were analyzed by metallographic microscope, scanning electron microscope (SEM), and energy dispersive spectroscopy (EDS). The corresponding casting billet defects were also analyzed. At the same time, the on-site process investigations were conducted to examine the production-related factors. The characteristics, causes, and process control measures of the black spots and linear warping defects were discussed. The results showed that no abnormal inclusions or inclusion segregation were found at the locations of black spots and linear warping defects on the hot-rolled plate surface. Instead, obvious secondary oxidation, decarburization, and grain growth phenomena were observed, along with the segregation of copper, boron nitride, and aluminosilicate inclusions at the defect areas. The black spots and warping defects were caused by the uneven deformation of the star-shaped cracks and corner cracks in the continuous casting billet during the hot rolling process. These cracks were related to the detachment of copper coating in the continuous casting mold, the segregation of aluminosilicate inclusions, and the segregation of boron nitride at the grain boundaries. Based on the above analysis, corresponding control measures were taken for the steelmaking and hot rolling processes, resulting in a reduction of the defect occurrence rate from 2.48% to 0.85%.