Rosa transmorrisonensis Hayata and allied taxa (Rosa section Synstylae) in Taiwan was extremely controversial in classification. The marked discrepancy between previous taxonomic treatments suggests that more intensive taxonomical investigation is needed. The present study revised Rosa transmorrisonensis Hayata and allied taxa based on extensive field observation and detailed morphological comparison. Our studies revealed that stipules, styles and terminal leaflets shape are the important and good characters for classifying Taiwanese taxa. As a result, Rosa sambucina var. mushaniana Liu & Ou and R. luciae var. rosea Li are considered to be synonymous with R. pricei Hayata. Rosa multiflora var. formosana Cardot is treated as a synonym of R. transmorrisonensis Hayata. Moreover, the identity of a puzzling taxon, R. taiwanensis Nakai, which had long been misidentified as R. pricei or misapplied the name as R. multiflora, R. luciae, or R. kwangtungensis, is clarified. The present study provides key to taxa, description, distribution, and illustration for each taxon.