Factors affecting photodegradation of Atrazine in the soil surface under UV light have been studied. Its degradation rate constant was determined to be (0.09~0.17)/min, photolytic depth 0.1~0.3 mm and half-life 4~8 min. The results show that soil granule size, pH, humidity, organic matter, humic acid and surfactant all could affect the photolysis of Atrazine in soil.