Aegistasubchinensis (Möllendorff, 1884) is a widely distributed land snail species with morphological variation and endemic to Taiwan. Three genetic markers (partial sequence of the mitochondrial cytochrome c oxidase subunit I [COI], the 16S rDNA and the nuclear internal transcribed spacer 2 [ITS2]) were analysed to infer phylogenetic relationships and genetic divergence of closely related species of the genus Aegista, Aegistavermis (Reeve, 1852) and Aegistaoculus (Pfeiffer, 1850). A new species from Aegistasubchinensis has been recognized on the basis of phylogenetic and morphological evidences. The nominal new species, Aegistadiversifamilia sp. n. is distinguished from Aegistasubchinensis (Möllendorff, 1884) by its larger shell size, aperture and apex angle; wider umbilicus and flatter shell shape. The northernmost distribution of Aegistadiversifamilia sp. n. is limited by the Lanyang River, which is presumed to mark the geographic barrier between Aegistadiversifamilia sp. n. and Aegistasubchinensis.