Abstract: As a new type of magnetic sensor, giant magnetoresistance (GMR) biosensor combines GMR effect and immunomagnetic microsphere technology, showing great application potential in biomedical and food safety fields. This paper reviews the basic principles of GMR biosensors, structural technology development, and applications in biomedical and food safety fields. The GMR biosensor realizes the detection of target biomolecules by monitoring the sensitive resistance change caused by the magnetic microsphere magnetic field. Its high sensitivity and low detectable concentration characteristics help to achieve quantitative detection of trace target molecules in biological samples. In the biomedical field, GMR biosensors have been applied to the diagnosis of cancer, viral diseases and other diseases, as well as genotyping. In the field of food safety, GMR biosensors are used to detect foodborne toxins and pathogens, as well as other food-related biomarkers. As technology advances, GMR biosensors will play an increasingly important role in ensuring food safety and public health.