The present study was conducted to evaluate the performance of five mulberry varieties used for rearing the bivoltine race (EJ) of mulberry silkworm. Nutritional composition of the leaves was determined. Carbohydrate/protein (C/N) ratios were focused. Also, leaf/cocoon ratios and its suitability for judging the mulberry leaves efficiency were determined. The results show significant differences between varieties. Kokuso-27 and Kearyang-Seoban-3 show higher nutritional components followed by Josaengrok-2. While the lowest value were recorded in Morittiana and Kokuso-20 varieties. Kokuso-27 and Kearyang-Seoban-3 recorded lowest values in C/N ratio and in leaf/cocoon ratio, and therefore, Kokuso-27 and Kearyang-Seoban-3 give more superiority over other varieties, they can be used as criteria for comparing the different mulberry varieties. The biological and economic characters of silkworm were reflection of higher values of leaf nutritional contents, lower values of carbohydrate/ protein ratio and leaf /cocoon ratio.