One of the biggest problems encountered during the last phase of silkworm rearing is non-uniform maturation of the silkworms especially during cooler months. Phytoecdysteroid (20-hydroxy ecdysone) was extracted in large-scale from a plant belongs to Caryophyllaceae and fed to silkworm larvae to test the effect of phytoecdysteroid. About 80％ of the silkworms were ready for mounting by 18 hrs after treatment (when the treatment is done for uniform spinning), whereas in control batch only 37％ worms were ready for mounting by the same time.