The invention relates to a method and an application for extracting an alexandrium tamarense inhibitor from enteromorpha. The method comprises the following steps of: lixiviating per
kilogram of the enteromorpha by using 2-5 liters of
distilled water at
room temperature for 12-72 hours, filtering to take filter liquor, and concentrating the obtained filter liquor into pastes by adopting a rotary
evaporation method; dissolving the concentrated pastes by using a mixing solution of
petroleum ether and 90 percent of
alcohol which are in a 1:1 ratio; sufficiently oscillating for 1-3 minutes, then demixing by standing for 10-120 minutes, and taking a lower-layer
alcohol phase; decompressing, evaporating and concentrating the
alcohol phase to obtain a paste-like substance at 40 DEG C; extractingand separating by using
ethyl acetate and secondary
distilled water which are in the 1:1 ratio, wherein a
ethyl acetate phase is the alexandrium tamarense inhibitor; and determining the volume of thealexandrium tamarense inhibitor extracted by per
kilogram of the enteromorpha to 50 milliliters. The invention is used for inhibiting the growth of alexandrium tamarense by adding 0.5-5 milliliters of the alexandrium tamarense inhibitor to per
cubic metre of a
water body, sufficiently utilizes the enteromorpha, has efficient economy, good
ecological safety and easy operation and control, effectively inhibits the growth of the oceanic alexandrium tamarense and particularly inhibits the growth of gymnodinium breve.