$xZrO_2-(1-x)SiO_2$ glass precursor with relatively high concentration of zirconium propoxide in metal alkoxide solution was obtained by sol-gel method and then heated at various temperature from 500 to $1,100^{circ}C$ to investigate the effect of the thermal treatment on the crystalline structure of the glass precursor. Based on X-ray diffraction analysis, the crystalline peak was started to develop at temperature higher than $600^{circ}C$, and the crystalline phase was considerably increased at $850^{circ}C$ or higher. With increasing the thermal treatment temperature, the characteristic peaks, such as baddelyite, tetragonal-$ZrO_2$ and zircon, was shown at $35^{circ}$, $50^{circ}$ and $60^{circ}$ of $2{ heta}$.