The ground and many excited states of the Mg+He van der Waals molecular system have been explored using a one-electron pseudopotential approach. In this approach, effective potentials are used to consider the Mg2+ core and the electron He effects. Furthermore, a core core interaction is included. This has reduced the number of active electrons of the Mg+He, to be considered in the calculation, to a single valence electron. This has permitted to use extended Gaussian basis sets for Mg and He. Therefore, the potentianl energy and dipole moments calculations are carried out at the Hartree-Fock level of theory, and the spin orbit effect is included using a semiclassical approach. The core-core interaction for the Mg2+He ground state is included using accurate CCSD(T) calculations. The spectroscopic constants of the Mg+He electronic states are extracted and compared with the existing theoretical works, where very good agreement is observed. Moreover, the transition dipole function has been determined for a large and dense grid of internuclear distances including the spin-orbit effect.