Abstract:High manganese non-magnetic steel plays an important role in the fields of electric power, transportation, aerospace and national defense because of its non magnetism and excellent mechanical properties. However, the non magnetism of the steel is not good in the actual production. The microstructure, phase composition of high manganese steel were studied using optical microscope and X-ray diffractometer, and the relative permeability of the steel was measured. The cause of residual magnetism for high manganese steel was analyzed. Results show that the samples after heat treatment at 1 200 ℃ are almost completely austenite, the content of residual ledeburite is low, and the non magnetism properties are better.