Abstract:The purpose was to investigate genetic diversity of Sargassum horneri populations in the coastal areas of Zhejiang Province, China. The 5.8S rDNA-ITS sequences from 44 individuals of S. horneri were amplified by PCR and analyzed, including wild populations from Huokun'ao of Nanji Island, Dongtou Island and Gouqi Island and Mazuao cultured population from Nanji Island in Zhejiang Province. The whole-length of sequence from all individuals was 1485 bp, including partial ITS1, ITS2 sequences, and complete 5.8S rDNA sequence. Among them, there was only one variable nucleotide site. It was suggested that there was no distinct genetic differentiation among populations with relatively low genetic diversity. In addition, 5.8S rDNA-ITS sequences from two haplotypes with the only one variable nucleotide site and another two sequences from GenBank public database were aligned, 31 variable nucleotide sites were detected, and 10 of them were insert or delete sites. Therefore, it was proposed to speed up the construction of artificial S. horneri field and restore wild S. horneri field in order to maintain an ecological balance.