The IPTG-inducible expression vector containing the BYDV GAV coat protein gene was constructed and transferred into E. coli BL21(DE3). High-level expression of the specific protein was achieved by IPTG induction. The results of SDS-PAGE and Western blotting show that the expression product which accumulates 19.5% of the total cellular proteins estimated by scanning is 24 kD BYDV GAV coat protein plus eleven amino acids of pET-5a.