Abstract: Magnetic hardness tester which appeared in recent years was a new type of portable hardness tester, and it can be used to test the hardness of large heat treatment parts in the field. The principle, structure, typical products at home and abroad, relative domestic and foreign standards, and application instances of magnetic hardness testers were introduced. The practical application shows that the magnetic hardness tester which applies Brinell and Rockwell test principle has reliable traceability. It has features of high accuracy and simple operation, providing important test methods for field fast and accurate hardness testing of large metallic parts. The wide application of magnetic hardness tester will dramatically improve the technical progress in some certain industries and enterprises.