Based on density functional theory, we investigate theoretically the stacking effects on the stabilities, electronic structures and optical properties of tin dichalcogenides SnX2 (X = S and Se) bilayers. Numerical results show that crystal-type SnX2 stacking pattern is the most stable bilayer structures with the least equilibrium interlayer distance. The electronic structures are dependent highly on the stacking patterns and interlayer distances. The band gap values can also be engineered effectively from 2.083(0.964) to 2.229(1.137) eV by forming five different SnX2 stacking patterns. Moreover, the imaginary part and real part also presents the anisotropic characteristics for all considered stacking cases. (C) 2015 Elsevier B.V. All rights reserved.