Abstract: By means of ultrasonic flaw, macroscopic low-magnification detection, chemical analysis, metallographic analysis, and scanning electron microscopy fracture analysis, the nature of defects in the production process of large-section carburized gear shafts was studied. It was found that the nature of the defects was hydrogen-induced white spots. Samples were taken at the defect sites for research, and analysis and prevention and control plans were developed. Process tests were conducted to explore the mechanism of hydrogen embrittlement white spots, and then smelting and heat treatment measures were adopted to achieve the purpose of process improvement.