During 2021-2022， two awl nematode populations were collected from the Guangdong Zhanjiang Mangrove National Nature Reserve and the Guangdong Zhenhai Bay Mangrove National Wetland Park， respectively.To investigate the phylogenetic relationships among closely related species of Neodolichodorus， morphological， molecular and phylogenetic analyses were conducted.These analyses confirmed that both populations were identified as Neodolichodorus sinensis.The 18S rDNA and 28S rDNA D2D3 region sequences were obtained for the Zhanjiang and Zhenhai Bay populations of N.sinensis， and phylogenetic trees were constructed based on these sequences.The results showed that in the phylogenetic tree based on 18S rDNA sequences， N. sinensis formed a highly supported monophyletic clade with N. persiangulfus.In the phylogenetic tree based on the 28S rDNA D2D3 region sequences， N. sinensis clustered with N. persiangulfus and N.bachlongviensis in a highly supported monophyletic clade.This study clarifies the relationships between N. sinensis and its closely related species.This paper identifies N. sinensis and N. persiangulfus as sister cryptic species.