The influences of lattice parameter of austenite, the electron concentration, the yield strength of parent phase on γ→εmartensite start temperature Ms in the Fe-Mn alloys containing C, Al, Ge and Si have been experimentally investigated. Theresults show that the lattice parameter of austenite is more important than the electron concentration and the yield strength ofparent phase in governing the γ→ε martensitic transformation in Fe-Mn based alloys. A relation between the Ms and latticeparameter of austenite in Fe-Mn based alloys is suggested. The elements Mn, C, Al, Ge, which increase the lattice parameterof austenite lower the Ms; while the element Si, which decreases the lattice parameter increases the Ms. The depressing effectof antiferromagnetic transition on the γ→ε martensitic transformation may be related to the increase of lattice parameterdue to the positive magnetostriction during the antiferromagnetic transition.