A mixture of vitamins in the cocoon yield of silkworm, Bombyx mori L. (Chinese hybrid-9f7x) was studied. Vitamins concentrations were 2, 4, 6 and 8 mg/ml. Results showed that; the concentration was 8mg/ml. of the mixture of vitamins was the best treatment. The weights of fifth instar larvae were 2.125 g when compared to 2.000 g in the control,  the weights of pupae recorded 0.800g compared to 0.711g  in the control, mortality percentages of the fifth instar were 6.25% when compared to 7.50% in control, durations of the fifth instar larvae were 9.15 day comparing to 9.65 days in control, percentages of cocooning were 93.69% comparing to 90.05% in the control, the productivity of silk was 2.38 cg/day comparing to 1.89 cg/day in control, weights of cocoon were 1.186 g, comparing to 1.031 g in the control, weights of cocoon shell were 0.218 g when compared to 0.183 g in the control and ratio of cocoon shell were 18.38% compared to 17.74% in the control.