The invention provides a multilevel structure titanium dioxide nanowire array and a preparation method thereof. The multilevel structure titanium dioxide nanowire array is an array consisting of titanium dioxide nanowires; and the titanium dioxide nanowires are of multilevel structures and comprise titanium dioxide monocrystal nanowires and titanium dioxide nanoparticles coating the surfaces of the titanium dioxide monocrystal nanowires. The surfaces of the titanium dioxide monocrystal nanowires are coated with the titanium dioxide nanoparticles, and the formed array is of high specific surface area and packing density, so that the electrochromism performance, capacitive performance, photoelectric property and the like of the array can be improved.