[Aim]  To develop an accurate and rapid method for identifying instars of the aphid Megoura crassicauda. [Methods]  A stereo microscope was used to record the body length and body color, body width, head width, antenna length, hind tibia length, cornicle length, and caudal shape and length, of different M. crassicauda instars. [Results]  Seven morphological indicators differed significantly among different instars (P<0.05). The antennal length of apterous and alate individuals from different instars did not overlap, and can therefore be used to definitively identify instars. Body length and hind tibia length can be used as auxiliary indicators. In addition, the presence of wing buds, the shape of the cauda, and the number of antennal subsegments, can also be used for rapid and specific instar identification. [Conclusion]  Antenna length can be used as the primary means of identifying the instars of M. crassicauda. When this is combined with the number of antennal segments, body length and color, hind tibia length, and the shape of caudal and wing bases, it is possible to accurately and efficiently identify the different instars of this species.