Male accessory glands and ejaculatory duct of Drosophila melanogaster are reproductive organs which synthesize secretory seminal proteins. Several products of these organs involved in egg laying, receptivity, and sperm stability or storage were isolated from their lumens. Despite their secretory process play an important role, exocytosis pathway in these organs is not well known. In the present study, we characterized secretory protein profiles and determined their secretory mechanisms. Eight accessory gland secretory proteins and two ejaculatory duct secretory proteins were detected in their lumens. All these proteins were constitutively synthesized in these organs and secreted to their lumens. Secretion of newly synthesized proteins initiated at about 1 h after synthesis, and reached the peak at 4 h after synthesis. It seems that secretion of the proteins may occur via constitutive exocytosis pathway.