It is generally believed that cliffs bear low biodiversity because of its harsh habitats. However, another reason, i.e. insufficient investigation caused by the inaccessibility of the cliffs, could not be excluded. In the genus Aster, two cliff species, Aster fanjingshanicus and Aster tianmenshanensis, respectively growing on the slate and limestone cliffs, were established. During our extensive field investigations, the third cliff species of Aster growing on granite cliffs from Eastern China was found. Based on the evidence from molecular phylogeny, morphology, and micro-morphology, we proposed that it should be treated as a new species and named Aster sanqingensis. It is described and illustrated here. Considering its limited number of individuals, highly localized distribution, and disturbed habitat, we proposed to treat it as a critically endangered species. Our new finding indicates there is cryptic biodiversity on the cliffs remaining to be discovered.