The electronic properties of an MoS₂ and graphene heterostructure are investigated by density functional calculations. Our results show that both the intrinsic properties of MoS₂ and graphene at the equilibrium interfacial distance are preserved in the weak van der Waals contact. Furthermore, Schottky doping for the MoS₂ and graphene contact can be tuned by the interfacial distance. Our calculations show that the Schottky doping can be transformed from an n-type Schottky contact to a p-type Schottky contact when the interfacial distance decreased. We find that interfacial charge transfer and the Fermi level shift determines the Schottky barrier transition from an n-type Schottky contact to a p-type Schottky contact. Our studies may prove to be instrumental in the future design and fabrication of van der Waals based field effect transistors.