Baculovirus re-infection to already-infected insect cells was assessed by comparing the binding of radio-labeled AcMNPV to Sf-9 cells with the expression of marker proteins, beta-galactosidase and variant of green fluorescent protein, respectively coded in the baculoviruses. The binding of baculoviruses to virus-infected Sf-9 insect cells was significantly inhibited with the elapse of time post primary infection (ppi) and completely inhibited by 12 h-ppi. The protein analysis suggested that baculoviruses bound to already-infected cells were internalized into the cells and routed for protein expression. However, the yield of protein coded in 2nd viruses (for re-infection) decreased with delaying re-infection time from the infection with primary viruses, and the expression of 2nd virus protein was not determined on the reinfection at 12 h-ppi. On the contrary, the expression of primary virus protein was inhibited by bringing forward the time of re-infection with 2nd viruses, giving nearly a steady level of total volumetric productivity.