In this study, a total of 40 tests of the toxicity of 8 halogenated benzenes to five algal species were performed. The result demonstrated that the toxicity of halogenated benzenes to five algal species was directly related to the hydrophobicity of the chemicals and the lipid content of the algae. Based on the results, we developed a K(ow)-based quantitative structure-activity relationship (QSAR) model: log(1/EC₅₀) = 1.050 logK(ow) + 1.429 log(1/lipid)-3.224 with n = 40, r² = 0.946, S.E. = 0.211, F = 323.933 at p < 0.001. This model provides evidence that the toxicity of halogenated benzenes to these five algae tested is related to the slower transference into lipid. This model can potentially be generalized to other algal species and toxicants.