Expression products of baculovirus expressing system are generally considered to be well immunogenic and possess the ability to assemble empty viral capsid. When the same FMDV expression cassette were expressed in E.coli and baculovirus expression system, the expression products from baculovirus excels that from E.coli in terms of the immunogenic [25] and protective effects [26] . Empty capsid comes into being only when capsid precursor P1-2A, protease L and 3C coding region from FMDV O1K serotype were all expressed in baculovirus expressing system(AcMNPV-Sf cell). Truncated protease L can not be selfcleaved from VP0. But, the expressed protease L is harmful to host cell growth, reducing the expression efficiency [27] . In adenovirus expression system, P12A3C expression cassette, including full structure of P1-2A,3C and portion of 2B and 3B, can be expressed and assembled into empty capsids [8] . Myristoylation of the animo terminus of P1-2A is of great importance to the assembly of viral particles [28] . It has been reported that the expression products of AcMNPV-Sf cell can be myristoylated well [29] . Based on the above studies, and using the design previously published by Mayr et al [8] , the P12A3C expression cassette of FMDV serotype Asia I was constructed. After two sorting rounds of recombinant virus and measurements of expression efficiency for more than 20 viral clones, the over-expressed recombinant virus Bm-P12A3C was obtained. It can express with very high efficiency in the hyperexpression variety of silkworm (JY1). The specific antigen produced per milliliter in silkworm haemolymph at least 100 folds more than the BHK-21 cell vaccine which had a PD 50 value of 3.6.