The content of domoic acid in water and in the body of some aquatic animals was detected by HPLC in order to find out the pollutant condition. The result showed that HPLC analysis was a simple and effective method for determining domoic acid in water and aquatic animals. Domoic acid has been found in some marine shellfish and not in seawater or freshwater. It is necessary to strengthen monitoring the contamination of domoic acid to prevent the toxin poisoning.