The high pressure of hexagonal-tungsten oxide (h-WO3) has been studied in diamond anvil cell up to 50 GPa at room temperature by angle-dispersive X-ray powder diffraction (AD-XRD). Cell refinement, FWHM and area of peaks and microstructure were analyzed. Results show that below 10 GPa, lattice strains follow linear trend, with bulk modulus B0 = 42(2) GPa, and its pressure derivative B0' = 13(2), and the crystalline grain sizes rapidly decrease in this range. In the range of 10–36 GPa, the lattice strains deviate linear trend, with decreasing amount of crystalline regions, and r.m.s. microstrain dominates this range. After 36 GPa, the lattice strain show a little increase, implying the crystalline-amorphous transformation occurs.