The Bm-P12A3C virus was inoculated 1,000 silkworms. The dying silkworm's haemolymph was collected (about 4-5 d post infection, corresponding with rearing mean temperature about 25-27uC). Sandwich-ELISA was conducted to evaluate the expressed antigen in silkworm. The results indicated that OD value of the harvested haemolymph from silkworm infected by Bm-P12A3C decreased as the dilution rate increased, which was in good agreement with variation of positive control of FMDV antigen. The expression yield was about 100 fold (positive antigen: 1/32,0.964; expressed antigen in haemolymph: 1/4096, 0.995) more than the positive control (BHK-21 cell vaccine which had a PD 50 value of 3.6), but was not detectable in the negative control (BmBacPAK-6 infected silkworm's haemolymph) (Fig. 2) .