Abstract: In the trial, MTF methods was applied to examine cytotoxie activity of dandelion extract in vitro on mouse maerophages after stimulated by lipopolysaccharide （LPS）, the objective was to determine the dose of non-cytotoxicity, meanwhile nitric oxide （NO） release in LPS-stimulated maerophages was determined by Griess method to provide a basis for further study. The resuhs showed that dandelion extract is not eytotoxic to LPS-stimulated macrophages with the dosage of no more than lmg/mL. 0.25-1 mg/mL dandelion extract has obvious inhibitory effect on NO release in LPS-stimulated mouse macrophages with the relation of dose-dependent and time-dependent.