This paper describes a novel and simple method to preparing monoclinic VO 2 (M) nanopowders via the reaction of ammonium meta-vanadate (NH 4VO 3) and oxalic acid dihydrate (C 2H 2O 4·2H 2O). The products were characterized by means of methods. XRD results show that well crystallized nanopowders of the monoclinic VO 2 (M) were successfully synthesized, while the molar ratio between NH 4VO 3 and C 2H 2O 4·2H 2O was kept at 1:0.5∼2.5, and the annealing temperature was 350∼750 °C for 2∼10 hour in nitrogen atmosphere. The spherical morphology of the samples is characterized by SEM. The crystallization temperature of the desired M/R-phase VO 2 is lower than 387 °C in this work. And the phase transition temperature is determined by differential scanning calorimetry (DSC).