Prisms-built VO₂(M) micro-nanostructures with narrow hysteresis width of 2.7 ℃ were successfully synthesized using V₂O₅-H₂C₂O₄-H₂O system by one-pot hydrothermal approach. The structure, composition, phase transition and optical properties were characterized by XRD, SEM, DSC, and variable-temperature UV-vis. The results revealed the prism had well-defined six facets and entire smooth surface with lengths of about 500 nm and thicknesses of around 100 nm. Several prisms were connected to each other through the apical growth. The prismatic VO₂(M) showed excellent phase transition and optical switching properties that would be beneficial for highly sensitive electrical/optical devices or other applications. The possible formation mechanism of prismatic VO₂(M) was proposed via time-dependent SEM images and XRD patterns. Furthermore, the influence of the amount of H₂O on the final product was discussed in detail.