The paper deals with two species of chitons of the genus Leptoplax, L. unica and L duongae sp. nov. collected in the South China Sea off the Spratly Islands. The new species differs from morphologically similar species of the genus by the sculpture of the jugum, absence of notch on the anterior margin of apophyses of the tail valve, rounded shape of pustules of tegmentum and distinctly ribbed dorsal girdle spicules.