Abstract: Single tube quantitative assay method for coliforms mensuration based on ONPG colorimetry had been established by our lab. Comparison between ONPG single tube quantitative assay method and lactose multiple tube fermentation technique was conducted by introduction these two method in coliform assay for bacterial suspensions prepared by the laboratory and natural seawater samples. The results showed that: no significant difference was found between the results of ONPG single tube quantitative assay method and lactose multiple tube fermentation technique; ONPG single tube quantitative assay method showed better accurateness, precision, and reproducibility than lactose multiple tube fermentation technique; ONPG single tube quantitative assay method was suitable for the rapid evaluation of coliform from water samples.