Recently, the discovery of intrinsic two-dimensional (2D) ferromagnetism has accelerated the application of spintronics in ultra-low power electronic device. Particularly, the Curie temperature of Fe ₃GeTe ₂can be improved to room-temperature in several ways, such as interfacial exchange coupling and ionic liquid gating, which makes Fe ₃GeTe ₂desirable for the practical application. In this work, we investigate the transport properties of Fe ₃GeTe ₂/graphene heterostructures with or without h-BN layers by utilizing the density functional theory combined with nonequilibrium Green’s function method. The results show that due to electronic orbital hybridization, the spin can be effectively injected into graphene with ± 0.1 V bias at the transparent contact interface of Fe ₃GeTe ₂/graphene. What is more, the efficient spin tunneling injection can be achieved in a wider bias range [–0.3 V, 0.3 V] by adding h-BN as a tunneling layer, where the spin filter effect that is induced by mismatched distribution of spin-dependent electronic states in the Brillouin zone, leads a spin polarizability to approach 100%. These results are helpful in the applications of 2D all-spin logic and the development of ultra-low power spintronic devices.