ABSTRACT Background: Natural silk is one of the best yarns that attract large number of users and become a very important industry. Mulberry leaves is a natural food of silkworm, therefore scientists have recently incorporating methods for increasing production of silk. These methods use the insect growth regulators (IGRs) or similar peptide hormones and amino acids to prolong the last larval instar to obtain large cocoon and high quality silk recipes. Results: The present investigation was carried during the spring (season 2018) to evaluate the effect of growth regulator pyriproxyfen at concentrations 1, 10 and 100 µg/larva on Bomobyx mori L., as well as, the effect of amino acid glycine 1% concentration solely or in combination with pyriproxyfen at the 5th day of fifth larval instar. Feeding 5th instar larvae of B. mori on mulberry leaves dipped in glycine 1% resulted in a significant increase in the weight of mature larvae and shorter larval duration, recording 5.12 g and 9.00 days, respectively. Meanwhile, the highest significant pupal weight (1.277 g) was attained when larvae treated topically with pyriproxyfen at 10 µg/larva in the 5th day in combined with glycine 1%. Regarding technological parameters, larvae which topically treated with pyriproxyfen at 10 µg/larva at 5th day and feed on mulberry leaves immersed in 1% glycine possessed the highest means of cocoon weight, cocoon shell weight, cocoon shell ratio, silk filament weight and size over other treatments. The total protein and ALT were attained a higher mean recording 78.433 mg/ml and 51.053 mg/ml for control larvae, successively. Meanwhile, it showed the lowest values for total carbohydrate and AST. Conclusion: The study showed that pyriproxyfen prolonged the 5th larval instar, while the use of glycine led to shortening the fifth larvae instar. Exposure to mixure of IGR and glycine, however, enhanced the parameters of silk compared with control. Key words: Bombyx mori L. , pyriproxyfen, glycine, biology, technology, silk filament.