The carbides/cementite plays a complicated role in the nucleation and growth of austenite during the austenite reversion of medium Mn steel. This study uses a relatively new orientation microscopy technique to characterize the nano-size carbides which forms during the austenite reversion in the Medium Mn steel. The Vincent-Midgley precession electron diffraction technique, along with automatic crystal orientation mapping in transmission electron microscopy (TEM) technique, is used to investigate the orientation relationship of the nanometre-sized precipitate with austenite ferrite matrix. This details TEM study raveled that the nano-sized carbides traps significant amount of Mn inside. As a result, it reduces the driving force for the austenite reversion. From crystallographic information it was concluded that these carbides were (FeMn)3C kind of non-stoichiometric cementite with similar lattice parameter to cementite (Fe3C).