The invention provides a novel determining method of the content of 
antigen virus of an 
inactivated vaccine of a recombinant 
bird flu H5N1 cellgen. The method comprises the following steps of: (1) preparation of MDCK (madin darby 
canine kidney), wherein 1.5ml of MDCK frozen 
cell with density of 2.0*10<6> is extracted and put in a water bath at a temperature of 37 DEG C, 10 to 15ml of 
cell culturefluid is added to culture for 72 hours, the 
cell is digested with 0.25 percent EDTA (
ethylene diamine tetraacetic acid)-pancreatin, the cell 
nutrient fluid is diluted into 
MDCK cell suspension of 4.0*10<5>, the 
MDCK cell suspension is spread to a 96-mesh 
cell plate in a 
cell density of 40,000 per pore (0.1ml per pore), the 
cell plate is put in a CO2 culture case at a temperature of 37 DEG C and 
humidity of 5 percent to culture for 24 hours to form a compact 
monolayer for later use; and (2) 
inoculation of a recombinant 
bird flu H5N1 
antigen, wherein recombinant 
bird flu H5N1 cellgen antigens in different batches are extracted and respectively added into the compact 
monolayer with 100mu l in each pore, and 100mu l of 
cell maintenance fluid is added to culture for four days, and a TCID50 (50% 
tissue culture infection 
dose) value is calculated by the number of cytopathic pores in a Reed-Muench method. The method is applicable to a cellgen vaccine for detecting the 
virus content by an erythrocyte 
agglutination test, which means that different viruses use corresponding sensitive cells.