[Aim] The ash whitefly Siphoninus phillyreae (Haliday), is one of the most important pests infesting fruit trees and ornamental plants worldwide. It is a recent invader to China. Morphological identification of this whitefly is complicated by its small size, high degree of similarity to related whitefly species and polymorphism. In the present study, a species-specific identification technique based on mitochondrial DNA cytochrome C oxidase subunit Ⅰ (mtDNA COⅠ) gene sequence (namely SS-COⅠ marker) was developed for the rapid identification of S. phillyreae.[Method] The fragments of mtDNA COⅠ gene of S. phillyreae and 11 other related whitefly species or cryptic species were amplified and sequenced using COⅠ gene universal primers LCO-1490/HCO-2198. One pair of species-specific COⅠ (SS-COⅠ) primers, SPZWCF1 and SPZWCR1 was designed. The length of target fragment amplified by this SS-COⅠ primer pair was identified and its specificity and sensitivity tested using various life stages and sexes of 11 whitefly species collected from two geographic locations.[Result] The primer pair amplified a 426 bp long fragment. The primer pair proved species-specific as it gave no cross-reactions against any of the 11 other whitefly species tested:five cryptic species of Bemisia tabaci (Gennadius) (AsiaⅠ, AsiaⅡ1, AsiaⅡ3, MED and MEAM1), Bemisia myricae Kuwana, Aleurodicus disperses (Russell), Aleurocanthus spiniferus Quaintance, Dialeurodes citri (Ashmead), Paraleyrodes pseudonaranjae Martin and Trialeurodes vaporariorum (Westwood). All S. phillyreae specimens were successfully identified. Sensitivity test demonstrated that the successful amplification could be obtained with 75.1 pg·μL^-1 template DNA, equal to 1/10240 of a whole female S. phillyreae adult.[Conclusion] The SS-COⅠ method developed here provides a rapid, simple and reliable molecular technique for the identification and monitoring of S. phillyreae, which would be benefit in intercepting and blocking the further spreading of this new invasive whitefly species.