Van der Waals (vdW) type metallic/semiconducting heterostructures have attracted much attention for applications like nanoelectronics. The electronic properties of graphene/SnSe2 vdW heterostructure are investigated by the first-principles calculation. The band dispersions of both the graphene and SnSe2 layers are well preserved in the graphene/SnSe2 vdW heterostructure. Notably, n-type Ohmic contact is found at the graphene/SnSe2 vdW interface so that graphene is a fantastic electrode for the SnSe2 Schottky barrier field-effect transistor (SBFET). The on-state current of the 10-nm-gate-long ML SnSe2 SBFET with graphene electrode is 1535 mu A/lm for high-performance (HP) application, which is twice that of the ML MoS2 SBFET with bulk Ti electrode and exceeds the requirement of the International Technology Roadmap for Semiconductors for HP devices.