Early damage is the main factor that causes the metal structures fracture suddenly. Aimed at the condition that most of the non-destructive testing methods can only be used to detect the macro-defect formed already, but cannot be used to detect yet to microscopic defects, the metal magnetic memory testing technology can only be used to qualitatively determine the location of the zone of stress concentration but can't be used to perform quantitative evaluation of the stress concentration zone, a method of combining simulation and experiment together is adopted to the research on the metal magnetic memory quantitative detection technology. A three dimensional force of Magnetic coupling model is established to simulate the three dimensional magnetic field distribution of the microscopic defects and research on the relationship between the stress, microstructure defect size, scan path of magnetic and magnetic memory signals. A metal magnetic memory testing system is constructed and the study of the relationship between the scan path and magnetic memory signals is performed. The experimental results and simulation conclusions are basically the same, and the use of the metal magnetic memory test technology can realize quantitative detection of the early microscopic defects.