On the basis of the chemical topological theory , Kier's molecular connectivity index (mX vp)and Hall's elect rotopological state index(En)o f 14 chloro -aniline compounds were calculated .The quantitative structure -bioactivity relationship (QSAR) between the acute to xicity of 14 chloro -aniline compounds to photo bacterium phosphoreum and En , mX vp was investigated with multiple regression analysis .By using stepwise regression analysis, the best QS AR model was set up and the correlation coefficient was 0 .979 .By using leave - one - out (LOO) of Jackknifed method , the model shows predictability and robustness , the estimated values are close to experimental datas.