The DFT-B3LYP method with the basis set STO-3G

6-31G*

6-311G** was employed to calculate the molecular geometric and electronic structures of 25 nitroaromatic compounds.Here three quantitative structure-activity relationship（QSAR） models were built by multiple linear stepwise regressions（LSR）.The estimation stability and generalization ability of these models were strictly analyzed by both internal and external validation and the best one was selected.Meanwhile

standard back-propagation algorithm of artificial neural network（BP） was used to establish a nonlinear QSAR model.The correlation coefficient（R2）

leave-one-out（LOO） cross validation R2cv

predicted values versus experimental ones of external samples R2ext of established LSR and BP models are 0.926

0.866

0.843 and 0.938

0.763

0.843

respectively.These show that the QSAR models have both favorable estimation stability and good prediction capability.The results indicate that there is a good multivariate linear relationship between the experimental values of the toxicity to Scenedesmus obliquus and the secondary lowest unoccupied orbital energy

the most positive net charge of the NO2

the energy difference between the highest occupied orbit and the lowest unoccupied orbit.