The better growth and development of silkworm Bombyx mori is dependent on nutrition. Nutritional value of mulberry leaves effects the larval growth. In the present study the silkworm larvae were fed on Spirulina supplemented mulberry leaves. Spirulina is blue- green micro algae containing 18 amino acids and vital vitamins. The weight of fifth instar larvae feeding on mulberry leaves and larvae before spinning was taken. The Spirulina increased the larval weight in experimental group as compared to control group.