Abstract: DNA samples of symbiodiniums from 26 species of Cnidaria, Spongiatia and Mollusca, and 1 species of pure culture symbiodinium were extracted by Chelex100 resin method. Twentysix valid sequences were obtained by PCR of chloroplast 23S rRNA. BLAST showed that these obtained sequences were consistent with target genes. This method has the advantages of small sample consumption, short operation time and low equipment requirements, and the avoidance of using toxic chemical reagents. It is an efficient and environmentally friendly DNA extraction method and will provide a technical reference for the molecular study of symbiodinium.