Transition metal phosphorus trisulfides, namely sulfides composed of three elements, stand out within 2D nanomaterials due to the unique layered structure, distinctive bonding, and electronic configurations. However, the preparation of ultrathin nanosheets encounters significant challenges due to the inherent properties of the material itself and the complexity of the synthetic process. In this work, we successfully fabricated ultrathin FePS3 nanoflakes with lateral dimensions of 500–800 nm and an average thickness of 5 nm utilizing mechanically assisted liquid-phase exfoliation in N-Methyl-2-pyrrolidone solution. The unique few-layer structure of FePS3 may increase the number of active sites, facilitating the rapid separation and migration of photo-induced charge carriers. Consequently, this enhancement leads to an increase in photogenerated current and a substantial reduction in resistance. This study presents an effective approach for optimizing light absorption and charge separation processes of 2D nanostructure, thereby providing valuable insights for the rational design of efficient photocatalysts based on ultrathin FePS3 nanosheet as a co-catalyst.