Prosperous silk production as well as quality of silk cocoon depend on the nutritional value of mulberry leaves and larval growth. The present study is carried out to evaluate the efficiency of whey protein on economic traits for silkworm, Bombyx mori L. Three concentrations from liquid whey protein (4, 6, and 8 %) were sprayed on mulberry leaves, also five grams from raw whey protein (powder) were used in feeding of 5^th instar larvae. Control larvae were feed on untreated mulberry leaves.  Result showed that, the highest mean of shell weight were (0.221, 0.216 and 0.203 g) recorded at concentration 4, 6 and 8% for liquid whey protein, respectively. The lowest mean of shell weight were (0.199 and 0.195 g) in raw whey protein and control, respectively. Highest growth index of larval of 5^th instar was recorded in liquid whey protein were (5.009, 3.901 and 3.364) at concentrations 8, 4, and 6% respectively.