A new species, Petrocosmea nanchuanensis Z.Y. Liu, Z.Y. Li & Z.J. Qiu from Mt. Jinfo at Banhe valley of Nanchuan District in Chongqing Municipality (China) is described and illustrated for the first time. Even though this new species is similar to Petrocosmea barbata, it has several significant morphological differences, which includes smaller leaves, repand leaf margin, densely appressed longer pubescences on both surfaces of leaves, larger flower with length of its lower lips about three times longer than that of the upper lips, oblong lower lip lobes, shorter pistil, ovate anthers and styles that are shortly pubescent or approximately glabrous above the middle. The distinct features of P. nanchuanensis and four relative species namely, P. barbata, P. longipedicellata, P. cavaleriei and P. xanthomaculata were also represented in depth. However, P. nanchuanensis is most closely related to P. barbata, based on molecular studies.