Photochemical degradation of linear alkybenzene sulfonate (LAS) using a pilot plant photoreactor is studied. LAS at 100 mg/L is degraded by UV-254 and UV/H2O2. Degradation of LAS is effectively enhanced by 720 mg/L H2O2. Moreover, the effectiveness of phototreatment on the biodegradability of LAS is examined. Both pretreated and untreated LAS are used in biological experiments. Combination of UV-254 with optimum concentration of H2O2 effectively enhanced the biodegradability of LAS. However, LAS at 100 mg/L can inhibit the growth of microorganisms. It is observed that the adaptation of activated sludge increases the biodegradation of LAS. However, due to the presence of intermediates in the effluent of the photoreactor, the biodegradability of this effluent is less than the biodegradability of the same as the concentration of untreated LAS. It is also observed that using the integration of UV/H2O2 and biological processes instead of single step of UV/H2O2, reduces the total residence time in chemical reactor while obtains the desired total efficiency.