Effect of Majorana  hortensis as food additives on rearing performanceof silkworm, Bombyx  mori L. was studied. Dried shoots of  M.  hortensis were soaked in heated water (60 ºC) for ten minutes to prepare different concentrations (0.1, 0.3 and 0.5 mg/ml.). The obtained results showed that, the concentration 0.5mg/ml. of M.  hortensis occupied the first category. Where 5^th larval instar weight recorded 2.039 g comparing to 2.003 g in control, pupal weight recorded 0.739g comparing to 0.692g  in control, 5^th instar mortality percentages were 5.00% comparing to 7.00% in control, 5^th instar larval durations were 9.33 day comparing to 9.54 day in control, cocooning percentages were 96.79% compared to 94.00% in control, silk productivity were 2.658 cg/day comparing to 1.866 cg/day in control, Cocoon indices were 1.255 g, 0.238 g and 18.96% for cocoon, cocoon shell weights and  cocoon shell ratio comparing to 1.000 g, 0.178 g  and 17.80% for the control, respectively.