Cultured shrimps are often exposed to different toxearing practices that may affect survival and quality of the product.Alexandrium tamarense, a dinoflagellate producing paralytic shellfish poison, on Chinese shrimp, A mouse bioassay (MBA) method was used to determine the toxicity of the extract from A. tamarense on studied. In addition, histopathology observation was conducted in gill and hepatopancreas after 96 h exposure to 1.0×10⁴ cells·mL⁻¹ and intramuscular injection with 20 µL the extract from was low, which was 3.950 of was , the safe concentrations were obtained, which was and the extract could cause some abnormal histological changes in gill and hepatopancreas, respectively, such as cellular swelling and vacuolated. Our study revealed that . Accordingly, the concentration of in the prawn ponds should be controlled below cells/mL at leastexposure. The lesions in the gills of that impedes the occurrence of gaseous interchanges isthemostlikelycauseofshrimp death after could cause thelesions in the hepatopancreas of