Weak magnetic detection technology is a nondestructive technique based on the magnetic-force coupling effect. By measuring and analyzing the magnetic signal on the surface of the material, the stress concentration, early damage, and degree of damage in the ferromagnetic material can be readily detected and evaluated. The main advantage of the weak magnetic detection technology include no manual magnetization or attached sensor, no surface treatment of component, simple operation and so on. Based on the weak magnetic detection technology in the past 5 years, a theoretical model of the technology was established and the progress made in the description and calculation methods of magnetic signals at defects, the damage assessment criteria in judging and locating defects, the progress of quantitative inversion of defects and so on. Finally, the engineering applications status of this technology was discussed. Based on this review, the future research directions of weak magnetic detection technology were proposed.