The degradation of formaldehyde and methanol by photo-Fenton method in a lab-scale reactor was investigated. It was found that formaldehyde and methanol decomposed with three stages. At the first stage, formaldehyde and methanol decomposed very rapidly and then were gradually slowed down at the second and the third stages. Three factors including initial pH, hydrogen peroxide concentration, and ferrous ions concentration were investigated in order to demonstrate their effect on the oxidation reaction. It indicated that the rates of formaldehyde and methanol oxidation were significantly increased with the increasing concentration of hydrogen peroxide and ferrous ions. While the initial pHs had slightly effect on the oxidation rate. In addition, at the higher concentration of methanol, the oxidation reaction of formaldehyde was obviously stopped. Moreover, the hydroxyl radical inhibition was occurred at the excess concentrations of ferrous ions. In this study, Fenton process was also conducted in order to compare with photo-Fenton process. It was found that UV-light had enhanced a higher oxidation efficiency at 0.0227 M of ferrous ions. With the exceeding concentration of ferrous ions, the oxidation efficiency of Fenton and photo-Fenton were insignificantly different.