A new fern species, Polystichum loratum H. He & Li Bing Zhang (Dryopteridaceae), is described and illustrated from limestone cliffs in northern Guizhou Province, China. Polystichum loratum is most similar to P. yaanense Liang Zhang & Li Bing Zhang in having narrowly ovate to lanceolate abaxial rachis scales. The new species is distinguished by its lorate leaf lamina, the oblong to narrowly ovate microscales (broad-type) on abaxial pinna surfaces, and the exindusiate sori, while P. yaanense has lanceolate leaf lamina, subulate microscales (narrow-type) on abaxial pinnae, and indusiate sori. Polystichum loratum is considered to be Critically Endangered (CR), based on IUCN Red List criteria.