Abstract: The principles of measuring retained austenite content in steel based on magnetic method were interpreted and an equipment for measuring the retained austenite content based on magnetic method was developed. This equipment included reversing method, throwing method and dynamic method. The ways of measuring the retained austenite content by reversing method and throwing method were different. The relationship between the retained austenite content and the strain in tensile state could be obtained continually and quickly by dynamic method. This equipment based on LabVIEW was a virtual instrument system which could acquit data, analyze data and had functions of visualization operation, automatic measurement, curve display and data storage. The residual austenite content of M50NiL bearing steel was measured by these three methods and the experimental results show that this equipment could accurately measure the retained austenite content in the steel.