Flexible photothermal devices have been extensively explored in a wide range of fields in recent years. In this work, a flexible photothermal nanocomposite film based on Ti2O3-PVA has been demonstrated for converting sunlight into thermal energy. Ti2O3 nanoparticles were surfaced-modified by four kinds of different surfactants (γ–aminopropyltriethoxy Silane, Hexadecyl Trimethyl Ammonium Bromide, Stearic Acid, Polysorbate-80), respectively, and then the nanocomposites were prepared by a simple solution casting method. The flexible composite shows strong sunlight absorption in a wide spectrum range (300 nm–2000 nm). Under illumination of 5 kW/m2 simulated sunlight, the nanocomposite can be quickly heated up to 64.1 °C. The nanocomposite presented stable performances after tens of bending tests, indicating good flexibility. Our results show that the nanocomposite with Ti2O3 nanoparticles modified with Stearic Acid exhibits the strongest light absorption capability and thus the best photothermal effect. This flexible composite material may have promising potentials in the applications of photothermal energy harvesting devices for wearable electronics, solar-driven steam generators, or seawater desalinators etc.