应用半经验量子化学计算方法,分析了2,3,7,8-四氯代二苯并二（口恶）英（2,3,7,8-TCDD）及其降解产物光激发后的电子跃迁类型,发现其紫外吸收图谱和阳光光谱有明显的重叠,光解是该类污染物的重要降解途径.通过计算2,3,7,8-TCDD及其光解产物光激发后化学键强度的变化和氢原子自由基反应描述符fR的数值,发现 UV-A和 UV-B辐射下反应以断裂 C-O键为主,而 UV-C辐射下脱氯产物增多;2,3,7,8-TCDD逐级光解脱氯生成三氯、二氯、一氯取代的异构体,并最终生成二苯并二（口恶）英;两个苯环上氯取代较多的一边更容易脱氯.2,3,7,8-TCDD及其脱氯产物也可以断裂C-O键,生成氯和羟基取代的二苯醚化合物,通过重排和进一步光解还可以生成氯取代联苯酚、苯酚以及多氯代二苯并呋喃. The semiempirical quantum chemical calculation method was used to analyze the electronic properties of 2,3,7,8-tetrachlorodibenzodioxin (2,3,7,8-TCDD) and its degradation products after photoexcitation Transition type and found that there is a clear overlap between UV absorption spectrum and sunlight spectrum, photolysis is an important degradation pathway for this kind of pollutants.Through calculating the intensity of chemical bond of 2,3,7,8-TCDD and its photolysis products The results show that the reaction of UV-A and UV-B radiation is dominated by cleavage of CO bond, while the dechlorination product is increased by UV-C radiation. The number of 2,3,7,8- TCDD photodegradation step-by-step to produce trichloro, dichloro and chloro-substituted isomers and finally to dibenzo-p-toluenesulfone; the two benzene rings are more easily dechlorinated on the more chlorine-substituted side. 2,3,7,8-TCDD and its dechlorination products can also cleave CO bonds to form chlorine- and hydroxyl-substituted diphenyl ether compounds that can also be produced by rearrangement and further photolysis of chloro-substituted diphenols, phenols, and polychlorines Dibenzofuran.