The morphology and infraciliature of a population of Pseudokeronopsis flava, a yellow-coloured ciliate collected from the coastal water near Zhanjiang, South China are investigated and described. Based on previous and present studies, an improved diagnosis is supplied: yellow to yellow-brown coloured marine Pseudokeronopsis, in vivo 140–350×30–50 μm with flexible and slender body; bicorona comprising about five pairs of frontal cirri; one buccal, 2–3 frontoterminal and 2–4 transverse cirri; midventral rows consisting of ≈30 pairs of cirri, which terminate subcaudally above the inconspicuous transverse cirri; about 50 adoral membranelles; left and right marginal rows separated at posterior end; 3–4 dorsal kineties; colourless, blood-cell-shaped cortical granules ellipsoid in shape, distributed over whole cell while yellow to yellow-brownish pigments positioned in a P. rubra-pattern; contractile vacuole positioned in posterior 1/4–1/5 of body; numerous macronuclear segments.