To reduce the manufacturing cost of human lysozyme (HLY) and thus spread its use in medicine, we designed, synthesized, and expressed the HLY gene in silkworm larvae by using a baculovirus system. The production of HLY in silkworms was highly efficient. N-terminal sequencing and mass spectrometry showed that it was physicochemically identical to natural HLY. The lytic activity of recombinant HLY in the silkworm hemolymph was 115 and 154 times that in yeast and silkworm cell culture systems.