Abstract: The marine diatom genus Pseudo-nitzschia Peragallo, the main biological source of Amnesic Shellfish Poisoning (ASP) - domoic acid (DA), has attracted great attention worldwide, and has became the hotspot in the research field of phycology and environmental toxins. Lots of progress has been made in the past two decades with 48 newly described taxa and 24 species that can produce DA. In China, a total of 17 taxa has been reported without any detectable DA from Chinese Pseudo-nitzschia strains. To investigate the species diversity of Pseudo-nitzschia in Chinese coast and the ability of DA production for Chinese Pseudo-nitzschia, monoclonal strains were isolated and established from Daya Bay, the South China Sea. These strains were identified based on the morphological characteristics by light microscopy and transmission electron microscopy and molecular analysis using the internal transcribed spacer region of ribosomal rRNA encoding gene, and the secondary structure of ITS2 RNA transcripts. We reported one newly recorded species for China, P. decipiens Lundholm & Moestrup. Its morphology was described and compared with both morphology-similar and molecule-close taxa, and the unique molecular feature of the secondary structure of ITS2-RNA was analyzed. No detectable DA was observed from this species using a single liquid chromatography tandem mass spectrometry (LC-MS/MS) injection. This study enriches the diversity of the genus Pseudo-nitzschia in China, and may provide detail information for the further studies about DA production of Chinese Pseudo-nitzschia strains.