Flame vapor deposition (FVD) process is the fast and effective method to prepare high quality 1-D nanostructured tungsten oxide thin film, which has several advantages in photoelectrochemical (PEC) water splitting such as more sunlight absorption, straight electron path and short diffusion length of electron hole. The precursor concentration in FVD process is the most important process variable to determine the morphology of prepared nanostructures. In this study, the precursor concentration in FVD process was controlled precisely and flexibly by adjusting the tungsten feed rate with the wire feeding device which we developed. Several interesting nanostructures were prepared in FVD process by modulating the precursor concentration with time and the reasonable growth mechanisms for developments of those nanostructures are also proposed. The narrower and longer 1-D tungsten oxide nanostructure could be prepared by controlling the precursor feed rate and deposition time in FVD process, which is desirable for efficient PEC water splitting.