The microstructure and mechanical properties of two high manganese austenite steels during tensile tests at roomtemperature were studied. The results indicate that the steels exhibit transformation induced plasticity(TRIP) and twinning induced plasticity (TWIP) under flow stress. At the initial strain rate of 10-3 s-1, the tensile strengths of 23.8％ Mn and 33％ Mn samples were 666 MPa and 540 MPa and their elongations were 67% and 97% respectively. In the range of initial strain rate of 10-310-1 s-1, nearly no strain rate sensitivity to flow stress in tensile test was observed, but such sensitivity was observed in plasticity. The steel, can be taken as the new generation highstrength and highplasticity automobile steel due to the better integrated mechanical properties.