The recent success in fabrication of free-standing perovskite oxide films, the thickness of which can be controlled at the atomic scale, breaks new ground in pursuing advanced low-dimensional materials. In this work, the structural characteristics and property modification of 2D (001) SrTiO3 nanosheets were investigated theoretically. Our results unveil that the system is subject to significant differentiation of Ti–O bonds and several competing structural phases; the properties are layer-dependent, and functionalities are more likely to emerge near the surface; the bandgap can be effectively adjusted by strain, but the in-plane strain has the opposite effect to the out-of-plane strain; electron-doping by V brings about magnetism without breaking the semiconductor nature while hole-doping by Al makes the system exhibit metallic and complex magnetic features. Our findings could partly explain the experimentally observed unusual flexibility and may be also useful to facilitate the understanding of 2D perovskite-based materials.