1-Methoxy-5-methylphenazinium methyl sulfate contains WST-8 [chemical name: 2-(2-methoxy-4-nitrophenyl)-3-(4-nitrophenyl)-5-(2,4-disulfonic acid benzene)-2H-tetrazolyl monosodium salt], which is reduced to a highly water-soluble yellow formazan dye by dehydrogenase in cells under the action of the electron carrier 1-methoxy-5-methylphenazinium dimethyl sulfate. The amount of formazan generated is proportional to the number of living cells. Therefore, this property can directly analyze cell proliferation and toxicity. The main uses of this reagent are drug screening, cell proliferation assay, cytotoxicity assay, and tumour drug sensitivity test.