• The microstructure of TiTe 2 /Sb 2 Te 3 heterostructure were characterized. • In-plane strain could be used to tune specific optical property. • Optical five levels were achieved firstly due to the resonant bonding effects. • Optical property changes arose mainly from charge density deviations at heterostructure Te...Te gap. [Display omitted] Heterostructural materials have the advantage of extreme low switching energy between states and hence are expected to be applied in photonic devices, whose optical performances are vital to explore in advance. In this paper, crystal structures of TiTe 2 /Sb 2 Te 3 heterostructural films and their effects on optical properties were clarified from the aspects of in-plane strain, resonant bonding and charge redistribution by experiments and first principle simulations. Larger strain in Sb 2 Te 3 sublayer tended to decrease reflectivity and refractive indexes, while huge resonant bonding effect was beneficial to improve the optical parameter deviations. Charge analyses showed that crystalline optical property variations were actually deriving from the electron redistribution differences especially near the heterostructural Te...Te gap, which also accounted for experimental reflectivity order. Finally, based on the resonant bond effects and surrounding electron density after stimuluses, five optical levels with identifiable optical contrasts (n and ΔR) were achieved in 1/2 model for uses. The present study sheds new light on optical properties of TiTe 2 /Sb 2 Te 3 and paves the way for potential multi-state applications of heterostructure in photonic and storage devices. [ABSTRACT FROM AUTHOR]