Abstract: The 48 h acute toxicity values of 40 substituted aromatic hydrocarbons to the algae were determined by using the standard method of OECD. The most toxic compound is 1,2-dinitrobenzene (lg 1/E^C50 is 5.04), while the least toxic compound is phenol (lg 1/E^C50 is 2.46). The energy of the lowest unoccupied molecular orbital ((E^LUMO)), the energy of the highest occupied molecular orbital ((E^HOMO)), Van der Waals area ((s^VdW)) and the molecular weight (M^w) of compounds studied were calculated by the quantum chemical method. Quantitative structure-activity relationships (QSARs) were developed with the toxicity and structural parameters of compounds. The toxicity of these compounds to the algae is related mainly to the orbital energy and the steric parameters. The equation (lg 1/E^C50=-1.029(E^HOMO)+0.025(s^VdW)-8.322, R2 (adj)=0.824) was found to fit well and the average relative error was 6.10% for the training set and 6.99% for the test set. Phenols and anilines are polar narcotics, and their toxicity could be related to the steric parameters or hydrophobicity; whereas nitrobenzenes are reactive compounds, may be regarded as pro-electrophiles, yielding the corresponding potentially highly toxic C-nitroso compounds, and their toxicity may be related commonly to the orbital energy. 更多还原