Eggs of castor silkworm are irradiated with different wavelengths of laser and they are made to produce the semilethal effect. After incubation, taking some blood from larva at the age of five, the spectra of its serum albumen is analysed. It has been confirmed that laser irradiation has a mutagenesis on heredity of castor silkworm. the mechanism involved with the relation of laser irradiation with gene expression, as adjuustion and control.