The present study aimed to assess the influence of soybean powder as a protein source added to mulberry leaves at three concentrations (1, 1.5, and 2 g / L water) on the biological and economic parameters of the silkworm, Bombyx mori. The experiments began from the beginning of the 4^th larval instar and extended to egg hatching that the emerged adult laid during spring season 2023. The obtained results showed non-significant difference between the three concentrations of soybean on silkworm characters. The weight of 4^th and 5^th larval instar was higher when larvae fed on 1.5 g and 1g of soybean respectively. The duration of 5^th larval instar was shorter when larvae fed on soybean 1g. Additionally, soybean 1.5 g gave the highest cocoon shell weight, while, 2g soybean gave the highest values of silk ratio and cocoon %. Furthermore, hatching percentages were high at soybean concentrations of 1.5 and 2 g, respectively. From the results obtained, it can be concluded that soybean with a concentration of 2g is the best concentration, as it gave the highest number of cocoons and silk ratio.