As a typical strongly correlated transition oxide, vanadium dioxide (VO₂) based nanomaterials have drawn many research attentions these years due to the giant metal-to-insulator phase transition (MIPT) at around 68 °C. However, due to the complexities of the V–O system and interplays between various vanadium oxide phases, the synthesis of high-quality VO₂ nanopowders is still fraught with many challenges, especially in air atmosphere. In this paper, we report a novel air atmosphere available liquid-shielding synthesis method for thermochromic VO₂ nanoparticles, by using low-eutectic molten-salt (LiCl–KCl) as the liquid-state air-insulation medium at elevated temperature and high-pressure pressed VOSO₄–KCl pillars immersed in these liquid salts as the precursor. Small amounts of glucose are added to introduce a slight reductive environment, and well dispersed VO₂ nanoparticles with excellent thermochromic properties can be directly synthesized at an ultra-low temperature of 375 °C. This feasible and atmosphere-available mass-production method is rarely reported in the related fields, which may provide a novel protocol strategy for the synthesis of high performance thermochromic VO₂ and other functional oxide powders.