Abstract: The Escherichia coli expression system is the most popular and frequently available system because its various recombinant proteins are economically and quickly obtainable. However, production of cell cycle proteins and toxic genes, in particular, expression of mammalian proteins would be difficult in that system. Baculovirus Expression Vector System (BEVS), which uses insect cells, offers more advantages than the E. coli expression system because most of the produced mammalian proteins retain their correct folding and activity. However, cell maintenance costs much time and expense. Our simple technique in BEVS has demonstrated its expression efficiency with such a high level that expression of C-SRC tyrosine kinase (CSK), an oncogenesis controllable protein, increased 2-3 times over that of cultured Spodoptera frugiperda Sf9 insect cells in 2 days than by the ordinary technique.