Crystal structure，magnetism，electronic structure，response to pressure and tetragonal distortions of stoichiometric Ni2MnSi were calculated by first-principles method based on the density functional theory within the projected augmented wave（PAW） appreach. The calculations show the contribution of the spin magnetic moments of Mn atom to the total moments is largest for Ni2MnSi. The low energy part of the total DOS is decided by Si-s-projected DOS, however, the high energy part of the total DOS is decided by the Ni -d-projected DOS, Mn -d-projected DOS and Si -p-projected DOS for Ni2MnSi. The entire energy surface for 095c/a2MnSi，which has significant implications for the growth and properties of thin films. We predict that the Ni2MnSi may also grow single crystal tetragonal structured thin film of ferromagnetic phase with high Curie temperature.