Indirect competitive enzyme-linked immunosorbent assay (ic-ELISA) was established to detect microcystin-LR in waters, with the concentration of the complete antigen was 5microg/mL, the dilution of the monoclonal antibody was 1:3,000, the dilution of the enzyme tracer (goat anti-rabbit IgG-peroxidase) was 1:3,000, the concentration range of microcystin-LR was between 0.001 approximately 30microg/L, and using o-phenylenediamine as substrate. The assay showed a high relativity of more than 99% with high performance liquid chromatography, a mean relative standard deviation less than 10% , a detection limitation under 0.01microg/L and quantitative detection range was 0.01 approximately 3microg/L, high specificity for [4-arginine] microcystin, and it could still perform well under the influence from the samples.