[Objectives]  To understand the morphological characteristics of Rastrococcus tropicasiaticus Williams and develop a taxonomic key to identify Rastrococcus species in the Oriental region. [Methods]  Random sampling, morphological observation and microscopic measurement were used to develop a quarantine and morphological identification method for the R. tropicasiaticus. [Results]  The taxonomic key developed in this study was instrumental to the first identification and interception of R. tropicasiaticus on longans imported from Vietnam. Single rows of ventral multilocular disc pores on the head and thorax and a few large dorsal quinquelocular pores were the diagnostic morphological characteristics used to identify this species. [Conclusion]  The key developed in this study can reliably identify R. tropicasiaticus and should therefore contribute to improved quarantine and identification of this pest.