In NiMnGa alloy the crystal structure of low temperature phase is strongly related to transformation temperature. In the present study three NiMnGa alloys with different transformation temperatures were studied. Alloy A has the martensitic start temperature (M s ) near ambient temperature and M s of Alloy B is near Curie point (T C ) whereas M s of Alloy C M s is well above T C . The crystal structures of three alloys were studied by X-ray diffraction in powder and bulk materials. The low temperature phase of single crystal in Alloy A was tetragonal phase with c a, and in Alloy C such a phase was tetragonal phase with c > a. The crystal structure of Alloy A in bulk material is in good agreement with powder diffraction, but in Alloys B and C there is a lack of conformity between bulk and powder. Furthermore, the difference of crystal structure in powder and bulk is discussed in more detail.