The Martensitic Transformation in Ferromagnetic shape memory alloys (FSMAs) can be triggered not only by changes in temperature and stress as that of paramagnetic conventional shape memory alloys, but also by changes in the applied magnetic field. It is well known that ferromagnetic shape memory alloy has diversified utilization, but not satisfactorily use, mainly because of high cost of processing and high cost of alloying elements. Among all Heusler alloy, Ni-Mn-Sn alloy have potential properties and exhibits lower cost. In this experiment Ni50Mn45Sn5 alloys characterize by using differential scanning calorimetric (DSC), optical microscope and X-Ray diffraction technique. The alloy undergoes the martensitic transformation from L21-type cubic structure into an orthorhombic structure.