This study aimed at improving the $TiO_2$ photocatalytic degradation of HA. In this study, the Degradation of Humic Acid using Jeju Scoria Coated with $WO_3/TiO_2$ in the presence of UV irradiation was investigated as a function of different experimental condition : photocatalyst dosage, $Ca^{2+};and;HCO_{3}_{-}$ addition and pH of the solution. Photodegradation efficiency increased with increasing photocatalyst dosage, the optimum catalyst dosage is 2.5 g/L and Photodegradation efficiency is maximized to $WO_3/TiO_2=3/7$. This indicates that $WO_3$ retains a much higher Lewis surface acidity than $TiO_2,;and;WO_3$ has a higher affinity for chemical species having unpaired electrons. The addtion of cation($Ca^{2+}$) in water increased the photodegradaion efficiency. But the addtion of $HCO_{3}^{-}$ ion in water decreased a photodegradation efficiency. Photodegradation efficiency increased with decreasing pH < pzc, the electrostatic repulsion between the HA and the surface of $TiO_2$ decreased.