Two new species of Microlaimidae: Microlaimus paraaffinis sp. nov. and Pseudomicrolaimus major sp. nov. are described from Yangma Island, the Yellow Sea. M. paraaffinis sp. nov. is characterized by body length 662–785 μm, six inner and six outer labial sensilla papilliform, four short cephalic setae 3–4 μm in length, amphidial fovea cryptocircular at level of buccal cavity, spicules L-shaped with equal thickness, gubernaculum boat shaped, tail conico-cylindrical with short cylindrical portion. P. major sp. nov. is characterized by large body size, six inner labial sensilla papilliform, six outer labial sensilla and four cephalic sensilla setiform, eight subcephalic setae present, amphidial fovea cryptospiral, anterior pharynx region at the buccal cavity widened, posterior pharynx region with oval-shaped bulb, spicules curved with proximal portion enlarged, gubernaculum boat shaped, tail short and conical. Pictorial key to genus Pseudomicrolaimus is given.