In this study, the influence of Ti content on the microstructure of the martensite bcc α ), which was formed by thermal effect, was investigated by scanning electron microscope and transmission electron microscope observations, in Fe-30Ni-xTi (x = 0.8, 1.8, 2.6) alloys. The crystallographic orientation relationship between austenite fcc (γ) and thermally induced bcc (α ) martensite was found to be as (111)γ//(011)α (Kurdjumov-Sachs (K-S)), by the electron diffraction analysis. The martensitic transformation temperature (Ms) of α martensite was determined as -41• C, -62• C, and -76• C in the alloys with 0.8%, 1.8%, and 2.6% Ti concentration, respectively. The Mössbauer spectrometer analysis has been revealed by a paramagnetic character for the austenite phase and magnetically order character for α martensite phase. Hyperfine magnetic field, isomer shift and volume fractions of phases were determined by the Mössbauer spectroscopy.