Abstract: A nondestructive testing technology based on weak magnetic principle was proposed to address the problem that existing nondestructive testing techniques were unable to meet the requirements of detecting multiple types of defects in wind turbine gears. Using the proposed method, the experiments were designed to detect two types of 17Cr2Ni2Mo steel samples with different defects, detection data were collected, signal processing and analysis were performed, and the results with industrial CT and Barkhausen noise detection were compared finally. The experimental results showed that weak magnetic detection technology was more sensitive to surface and internal crack defects of gears, had good recognition for grinding burns of gears, accurate positioning, and the results after signal processing were more-intuitive and clear. This method has the potential for application in nondestructive testing of wind turbine gears.