Abstract: Monostroma collected from Zhejiang Province and Guangdong Province was studied in this paper.  Identification was conducted by combining morphological observation and molecular biological methods. At the morphological level， the thallis were soft and slimy， their cross sections were flake， membranous and had monolayer cells. At the molecular level， the result of ITS sequencing analysis showed that all collected samples belonged to the same phylogenetic group， and were identified as Monostroma nitidum. There were two growth ways in M.nitidum: one was asexual reproduction， the other was sexual reproduction. M.nitidum was of great economic value， and it had good prospects for the development and utilization.

Key words: Monostroma nitidum, morphology, ITS, molecular identification