The DFT-B3LYP method, with the basis set 6-311G**, was employed to calculate the molecular geometries and electronic structures of 30 nitroaromatics. E_HOMO, E_LUMO, E_NHOMO, E_NLUMO, ΔE, E_T, Q_NO2, Q_C-NO2, Q_C-X, μ and V were selected as structural descriptors. According to the type and number of substituents, the acute toxicity (－log IC₅₀) of such nitroaromatics to Tetrahymena pyriformis along with hydrophobicity quantified by the 1-octanol/water partition coefficient (log K_ow) and the above eleven structural parameters, was used to establish the quantitative structure-activity relationships (QSARs). The results indicate that the frontier orbital energies have important contributions to the toxicity of those nitroaromatics, and the electronic transfer interactions between the chemicals and biological molecules are the chiefly toxic actions of the nitroaromatics to the Tetrahymena pyriformis. For mononitro derivatives, their toxicities were correlated to log K_ow too. The existence of halogen substituent may enhance the toxicities of such nitroaromatics. A highly predictive model was obtained for all objective compounds: －log IC₅₀＝18.037＋10.446Q_NO2 －41.323ΔE－20.471E_NLUMO＋24.989E_NHOMO with n＝30, R＝0.962, SE＝0.185, F＝78.640, Sig.＝0.000.

Key words: nitroaromatic, Tetrahymena pyriformis, toxicity, density functional theory, quantitative structure-activity relationship