We have revealed the influence of composition doping (Ni2+x Mn1-x Ga, Ni2+x MnGa1-x , and Ni2Mn1+x Ga1-x ) on lattice constants and atomic magnetic moments of austenite, 7 M and NM martensite, by ab initio calculations. It is demonstrated that Ni-doping decreases the volume, whereas Mn-doping increases it. The total magnetic moment of the three series of alloys is mainly dominated by their Mn content with little phase-state dependence. The perturbation of the magnetic moments by atom substitution is mainly dominated by the Mn environment. This study is expected to provide information on composition-related structure and magnetic properties of Ni-Mn-Ga alloys that could not be obtained by experiments.