Interlayer distance induced Rashba spin splitting is predicted in graphene and monolayer iodinated arsenene (As-I) van der Waals heterostructures based on first-principle calculations. The equilibrium structure of graphene/As-I exhibits a linear Dirac-like dispersion relation at K point in Brillouin zone. With the change of interlayer distance, large and tunable Rashba spin splitting can be realized from zero to more than 100 meV. Projected band structure analysis is performed, which indicates a strong relation between the extent of band splitting and the hybridization of C and As orbitals near the Fermi level. Meanwhile, charge density difference calculations reveal a pronounce charge transfer between graphene and As-I with varying interlayer distances, leading to the change of built-in electric filed along z direction that modifies the electronic structures significantly. Our work may make a special contribution to the realization and application of spintronic devices based on van der Waals heterostructures. (C) 2017 Elsevier B.V. All rights reserved.