Abstract: Bearings are crucial components in the equipment manufacturing industry, as their quality directly determines the safety and reliability of related equipment and products. This work proposes a magnetic testing technique for non-destructive testing of bearing crack defects. The methods involves applying an alternating magnetic field excitation to generate an induced magnetic field signal on the bearing surface, adjusting the excitation intensity to optimize the detection effect, and designing a fitting excitation device to adapt to the specimen surface. An independently self-developed magnetic testing equipment was used to conduct the research on artificial groove defects and natural crack defects of varying sizes, and quantitatively analyze the collected magnetic induction intensity signals. The results show a positive correlation between the peak-to-peak value of the magnetic induction intensity anomaly signal between the defect depth , and a negative correlation with the defect width . Namely, the higher the depth-to-width ratio of the defect, the greater the peak-to-peak value of the anomaly signal, and vice versa. Quantitative analysis of defects can be achieved through linear fitting of aspect ratio and peak to peak values of abnormal signals. This magnetic detection technology is used for rapid detection of bearing cracks and has high reliability and effectiveness.