Abstract: In this study, the group composition, abundance of meiofauna and species composition of marine nematodes were analyzed using investigation data of Qigu Lagoon of Taiwan in August 2022. More than five meiofauna groups and total of 491 species belonging to 11 families and 21 genera were identified, including free-living marine Nematode, Oligochaeta, Copepoda, Turbellaria, Polychaeta and other groups. Marine nematodes was the most dominant group, accounting for 78.52% of the total abundance. The abundance ranged from (4.79±2.50) to (492.04±416.79) ind./10 cm². Dominant genera of marine nematodes were Neochromadora, Haliplectus, and Terschellingia. The morphological data of the valid species in Eleutherolaimus were collected. A new record of free-living marine nematodes species, Eleutherolaimus paraschneideri, was described. The main differences between the new record species and model species were compared.