The structures of e martensite formed by different tensile strains in an Fe-16.56Mn-4.50Si-10.30Cr-5.29Ni alloy have been studied by TEM and HREM observations. When the tensile strain is less than 3%, martensite plates grow to reach a thickness less than 10nm and a length with certain size and the epsilon (M)/ Y interface at the growing front of epsilon martensite maintains good coherence. With increasing tensile strain, growing feature of self-excitation transformation gradually emerges and epsilon martensite grows by the formation of base units, therefore structure of the epsilon martensite becomes complicated. When the tensile strain is more than 3.5%, a lot of bands made of epsilon martensite plates and retained parent interlayer will be formed.