Celosia argentea seed (CAS) has been used as a traditional Chinese medicine for the treatment of liver damage and eye diseases. CAS is easily falsely harvested and misused, five species from Amaranthaceae family have frequently found to be involved in the adulteration and misapplication, namely Celosia cristata seed (CCS), Amaranthus tricolor seed (ATS), Amaranthus retroflexus seed (ARS), Amaranthus cruentus seed (ACS), and Amaranthus spinosus seed (ASS). For the purpose of identification, multiple morphological means including stereomicroscopy, scanning electron microscopy, normal light and polarized light microscopy were comprehensively employed. As a result, micromorphological and microscopic characteristics were extracted and a diagnostic key to CAS and its five adulterants was proposed for the first time. With respect to the genetically closely related species, viz. CAS and CCS, chemical means were developed to achieve the goal of precise identification. Firstly, triterpenoid saponins in CAS and CCS were fully characterized by an HPLC-QTOF-MS/MS method, a total of 20 triterpenoid saponins including 9 novel members were identified. Secondly, the HPLC-ELSD specific chromatogram was established, in which 12 common peaks were assigned. Finally, after a careful comparison, the peak area ratio of two triterpenoid saponins was discovered as interspecies discriminant marker. In conclusion, CAS and its five adulterants can be precisely identified by multiple morphological and chemical means.