Al/W co-doped VO2 with a monoclinic structure, space group P2(1)/c, was synthesized (hereafter, Al/W-doped VO2(M1)) and its thermochromic property was investigated. First, to prepare the precursor for Al/W-doped VO2(M1), V2O5, (NH4)(10)W12O41 center dot 5H(2)O, and AlCl3 center dot H2O were dispersed in a citric acid solution and then hydro thermally treated in an autoclave. Then, the Al/W-doped VO2(M1) powders were synthesized by heating the obtained precursor at various temperatures under an Ar gas flow. The Al/W-doped VO2(M1) has a monoclinic structure with space group P21/c, similar to undoped VO2(M1) and W-doped VO2(M1). The Al/W-doped VO2(M1) indicated that the monoclinic to tetragonal transition temperature was lowered to approximately room temperature by the Al and W doping. The Al/W-doped VO2(M1) had the lower optical band gap and showed a larger IR reflectance in the 800-2000 nm range, compared with W-doped VO2(M1) and pure VO2(M1).