According to the experimental synthesis of ZnTiO3 ferroelectric compound with LiNbO3 (LN) structure, the characteristics of the LN-ZnTiS3 compound were designed and studied based on the first-principles method. The calculated results show that the LN-ZnTiS3 compound meets the conditions of mechanical stability. According to the analysis of the chemical potential equilibrium phase diagram, LN-ZnTiS3 will not form a stable structure under normal pressure, but can form a stable structure under external pressure. The calculated density of states and energy band indicate that the valence band maximum (VBM) of LN-ZnTiS3 is mainly composed of S-p orbitals, while the conduction band minimum (CBM) is composed of Ti-d orbitals. The substitution of sulfur atoms can promote the electron state above Fermi energy level of the system to drop significantly to the lower energy level, thus reducing the band gap of LN-ZnTiS3. The calculated band gap of LN-ZnTiS3 is 1.04 eV, which can promote the absorption of visible light. It shows that LN-ZnTiS3 is a potential high-efficiency photovoltaic material.