The insect cell expression system is a commonly used eukaryotic expression system for expressing large-molecular proteins. Compared with mammalian cells, insect cell culture conditions are relatively simple and do not require CO2. Baculovirus is a kind of double-stranded DNA virus with insect cells as natural host. It has high species specificity, does not infect vertebrates, and is harmless to humans and livestock. sf9, the most commonly used as host cell, appears in planktonic or adherent in the culture. sf9 is very suitable for large-scale expression, and can be used for subsequent processing and modification of proteins such as phosphorylation, glycosylation, and acylation. The insect cell expression system can also be used for the expression of multiple genes, and can also express toxic proteins such as antimicrobial peptides.