Twenty species of Libnotes (Laosa) Edwards, 1926 are known worldwide and three are known from China so far. Here, two species of Laosa are added to the Chinese fauna, of which L. (L.) baiyunensis sp. nov. is described and illustrated as new to science, and L. (L.) fuscinervis Brunetti, 1912 is newly recorded from China. Morphologically, the new species is most similar to L. (L.) charmosyne (Alexander, 1958) but can be distinguished by the pleura of the thorax, the relative position of the additional cross veins in cell r3 and r5, and the details of the male genitalia. A key to the world species of Laosa is presented.