The characteristics of vitellin and its content in vitellogenesis were studied in Propylea japonica (Thunberg). The characterization of vitellin was carried out by PAGE and SDS-PAGE. The results indicated that vitellin had a molecular weight of approximately 294.81±40.70 kD and was composed of two subunits, whose molecular weights were 144.68±0.03 kD and 51.23±0.27 kD respectively. The content of essential amino acid was 57.48%, which was little higher than that of non-essential amino acid. The amino acid with the highest content in vitellin was Glu, its content was 15.26%; while contents of Trp and Met were very low, only 0.50% and 0.11%, respectively. Using indirect ELISA, the contents of vitellin in the fat body, haemolymph and ovary of P. japonica were detected. The results suggested that the vitellogenin was synthesized in fat body at the 2nd day after eclosion. The contents of vitellogenin in fat body, haemolymph and ovary increased quickly on the 4th day after eclosion and reached the peak stage approximately on the 8th day in adult stage.