Abstract: In order to investigate the diversity of free-living marine nematodes and improve the species list in China, this study carried out taxonomic and diversity analysis of free-living marine nematodes in the subtidal zone of the northern Yellow Sea. As results, three new recorded free-living marine nematodes i.e. Abelbolla maemulensis Hong & Lee, 2014, Sabatieria longisetosa Kreis, 1929, and Terschellingia distalamphid Juario, 1974, were identified. Among them, Abelbolla maemulensis is characterized by thin pointed front end. It is with six outer labial sensilla and in papillae form, dentate, right subventral tooth largest. the cervical setae are located about 2.0 hd from anterior end in one circle. The other cervical setae are about 5 µm long and arranged irregularly. Circular amphid with elongated corpus gelatum; pharynx expanding gradually and muscular along its entire length, without posterior bulbs; gubernaculum with dorso–caudally directed apophysis, with swollen distal tip; tail conico-cylindrical. The species Sabatieria longisetosa is characterized by cylindrical body; oral cup, toothless; spiral-shaped amphid after head setae. Ventral gland cells were located at 1/3 of the posterior end of pharynx. Spicule is short, and curved at an obtuse Angle; the gubernacular has a long dorsal tail process; six precloacal spine; tail conical column. The species Terschellingia distalamphid is characterized by long cylindrical, its head is truncated, its inner lip sensilla is not obvious, and its outer labial sensilla, with papillae form. It has four cephalic setae, four subcephalic setae. The amphid is round. The excretory system is remarkable. The pharynx is cylindrical and the base is enlarged to form a large pharyngeal bulb. Tail conical column. Spicules slightly curved ventrally, with a central diaphragm and gubernacular shaped like a tail. This study has added newly recorded species of marine nematode and enriched the species diversity information of marine nematode in China.