Loop-mediated isothermal amplification (LAMP)method was employed for rapid and simple detection of toxic Alexandrium.A set of four primers was specially designed on the conserved region of genus Alexandrium.By the detection system,target DNAs of toxic Alexandrium were amplified and visualized on agarose gel within 60min under isothermal condition at 65℃.The LAMP amplicon was also directly visualized in the reaction tube by addition of SYBR Green I for naked-eye inspection.The detection limit of this LAMP assay was 10-fold to conventional PCR method on the target DNA of Alexandrium minuturn.The LAMP assay reported here indicates the potential usefulness of it is a valuable,fast alternative procedure for the detection of targets toxic Alexandrium during coastal water monintoring,especially in its rapidity and simplicity.