The mechanical properties and microstructures of alternative low carbon TRIP-aided steels in which manganese contents mediate between conventional low-alloyed TRIP-aided steels and TWIP steel have been investigated. A variety of microstructures, from a single austenite phase to multiple phase mixtures, was attained according to chemical compositions as well as heat treatment schedule. By means of reverse transformation of martensite combined with controlled annealing, a remarkable grain refinement being responsible for stabilization of austenite could be achieved. In case of the duplex (+ ) microstructures in 6Mn and 7Mn alloys, large amount of retained austenite more than 30 % contributed to substantial improvement of ductility compared to the conventional TRIP-aided steels having similar tensile strength level. In nearly single austenitic 13Mn alloy, the annealed sheet steel exhibited high tensile strength of 1.3 GPa with sufficient ductility due to the stain induced martensite transformation of fine grained austenite.