Using recombinant Vaccinia virus(vSC8) that express ${eta}$-galactosidase, a model heterologous protein, conditions for virus and protein production were investigated in tissue culture flask. As host animal cells HeLa and HeLa S3 were used. It was demonstrated that cells infected during the exponential growth phase gave higher protein yield than those infected during the stationary growth phase and calf serum concentration after virus infection did not significantly alter protein yield. Pretreatment of cell layer with hypotonic solution enhanced the virus infectivity. Optimum cell growth and recombinant protein production was achieved at $37^{circ}C$. But, during 2 hours of virus infection period incubation temperature must be lowered to 20∼$30^{circ}C$ for maximum recombinant protein yield. To enhance virus replication, the effects of adrenal glucocorticoid hormone (Dexamethasone) and silkworm hemolymph were evaluated. Only dexamethasone increased about 20% of ${eta}$-galactosidase yield in HeLa S3 cells when added with 10-7∼10-5M concentration 24 hours before infection.