In order to reduce high phase transition temperature and improve low transmittance contrast in the infrared (IR) region before and after phase transition caused by doping, W-doped VO2 thin films with an obvious thermochromic behavior are fabricated by W-V co-sputtering on the glass substrates and annealed in a mixture of N2 and O2. Component and structure of VO2 thin films oxidized in different ratios of N2-O2 mixture are analyzed. Results reveal that VO2 grows in preferential crystal orientations along (011) and (200), and the particle dimension increases from 50 nm to 80 nm as O2 content rises. Phase transition temperature of W-doped VO2 thin films reduces to 31 ℃, transmittance contrast in the IR region before and after phase transition is 41%. Results demonstrate that proper W-doped concentration can reduce the phase transition temperature, improve IR transmittance spectrum and gently change the transmittance contrast.