The quantitative relationships between photolysis half-lives（t _1/2） and molecular structures of dioxins (PCDD/Fs) was described. Atomic characteristic value δi  of PCDD/Fs were defined. The topological descriptor Km and orientating group bedeck index mXJ were acquired by the technique of molecule graphics and AM1. The QSPR model，which could predict photolysis half-lives of PCDD/Fs adsorbed to spruce needle surfaces，were established using the index，the regression equations was proposed with mean deviation was 0.056. A modified leave-one-out procedure test was performed to validate model robustness，predicted the t _1/2  of other some PCDD/Fs molecules by the regression equation，and the error analysis were discussed. The results show that the model developed can make a better agreement between predicted and observed values of t _1/2.