We describe that the surface and thickness of nanoporous $WO_3$ fabricated by both light-induced and light-absent anodization are affected by pre-annealing process from $200^{circ}C$ to $600^{circ}C$. As a result, the nanoporous $WO_3$ with a thickness of $1.83{mu}m$ can be achieved by anodization for 6 hours after pre-annealing at $400^{circ}C$ without illumination of light. Moreover, the thickness of nanoporous $WO_3$ fabricated by pre-annealing is thicker than that of $WO_3$ prepared by non-annealing process. However, the light illumination during anodization leads to convert the crystalline structure obtained by pre-annealing, which interfere the growth of nanoporous $WO_3$. In this paper, we discuss about the growth mechanism of these different nanoporous $WO_3$ films.