Recently, the development of new photothermal materials for seawater desalination based on air–water interfacial solar heating has become a new research hotspot. In this paper, hydrophobic lithiated titania was synthesized by lithium reaction with amorphous titania followed by surface modification with a thin 1H,1H,2H,2H-perfluorooctyltrichlorosilane (PFOTS) monolayer. The hydrophobic lithiated titania was used as a photothermal material for seawater evaporation based on this new process. A thin lithiated titania floating film was assembled under simulated solar light irradiance due to the combined actions of water surface tension and the water molecules' thermal motion. The formation of the thin floating film significantly promoted water evaporation. The water evaporation rate by the lithiated titania floating film was 0.87 kg·m−2·h−1 under 2.0 sun solar irradiance, which was 2.4 times higher than that of pure water. Parameters affecting the solar evaporation process such as lithiated titania dose, solar light intensity, and storage time were investigated. Finally, the quality of the condensed fresh water was tested to evaluate the potential application of the lithiated titania floating film in practical settings of seawater desalinization.