Recently, various kinds of transgenic silkworms, Bombyx mori, which spin innovative silk, such as fluorescent or extremely thin one, have been developed. Practical application of the value-added silkworms can be a major solution to revitalize sericultural farmers, who confront low cocoon price. The use of transgenic organism is regulated by the Cartagena law in Japan on the purpose to conserve biodiversity. Silkworm itself is a highly domesticated animal which is unable to feed or reproduce under natural conditions without human care. It is unlikely that the introduction of the genes encoding genetically engineered silk enables the silkworm survive independently to become a threat to biodiversity through competition with wild animals or feeding on natural plants. The wild silkworm, B. mandarina, inhabiting Japan can cross with B. mori artificially but no hybrid has been identified in the natural population of Japan. One reason of the absence of hybrids is that moths do not emerge in sericultural farms because pupae are killed in their cocoons for silk reeling. It is also supposed that the silkworms discarded outdoor cannot grow to mate with their wild relatives. In this study, we found that both larvae and moths of B. mori were preyed rapidly under natural conditions by various predators, such as birds, wasps, ants, and carrion beetles. We also developed methods for the risk assessment of rearing transgenic silkworm on biodiversity and applied them to a transgenic silkworm strain producing fusion protein of fibroin and green fluorescent protein (GFP) of jellyfish (Aequorea victoria). In the measurement of walking distance of individual fifth-instar larvae in 16hours, no statistical difference was observed between transgenic and non-transgenic silkworms. We also compared the position of eggs laid by individual female moths after mating and obtained a result that transgenic silkmoths laid eggs in smaller area than non-transgenic ones. The production of allelochemical substances was also tested by biological assay. On the soil mixed with freeze-dried powder of larval body or feces, there were no statistical differences between transgenic and non-transgenic silkworms for the rate of germination or weight of the seedling. The number of bacteria and fungi was also compared after the incubation of the soil mixed with the powdered specimens, resulting in no statistical differences between transgenic and non-transgenic silkworms in most of the tests. In combination with conventional statistics in silkworm breeding, such as larval days, cocoon weight, and egg numbers, researchers can assess the risk of their transgenic silkworm on biodiversity for the application of permission to rear them in sericultural farms