The impact of turbidity, light source, pH value on degradation of 2, 4-dichlorophenol (2, 4-DCP) was analyzed to determine water quality limit with turbidity of aqueous solution less than 6NTU by UV/H_2O_2 photochemistry oxidation degradation. The removal rate of 20 mg/L 2, 4-DCP can be up to 95% in 90min by adding H_2O_2 dose 1.28 mg/L under UV power 30 W. UV/H_2O_2 photochemistry oxidation treatment was proved to be an effective approach to remove organic micro-pollutants in aqueous solution with low turbidity.