[Objectives]  To investigate the potential function of the mandibular gland of male Camponotus japonicus Mayr, which have the most developed mandibular glands among all castes of this species. [Methods]  The morphology, surface ultrastructure and internal characteristics of secretory cells of the mandibular glands of male ants at different ages were observed using a light microscope (LM), a scanning electron microscope (SEM) and a transmission electron microscope (TEM). Volatile mandibular gland secretions were extracted with n-hexane and analyzed using gas chromatography-mass spectrometry (GC-MS). [Results]  (1) The mandibular glands of males consist of a cluster of secretory cells and a reservoir. Each cluster of secretory cells contains a secretory cell and a conducting cell. The total length of the mandibular gland, reservoir length and the diameter of secretory cells, were largest in the 1st month after eclosion. Secretory cells were initially moist, full and smooth, but became progressively less so as males aged. (2) The cytoplasm of secretory cells contains a lot of organelles, such as mitochondria, endoplasmic reticulum, Golgi apparatus,  lipid droplets, other granular secretions and developed end apparatus. From the 1st to 4th month after eclosion, secretory cells have a low density of secretory granules, secretory vesicles gradually become more abundant and mitochondria surround the nucleus and microvilli. From the 8th to 9th month after eclosion, mitochondria become scattered among the nucleus, microvilli and secretory granules, the density of secretory granules increases, secretory vesicles disappear, and the cells began to disintegrate. (3) GC-MS analysis indicates that the least quantity of secretions was emitted during the 3rd month after eclosion and the most during the 9th month. A total of 23 volatile chemical components were identified, of which 2-hydroxy-6-methylbenzoate, Methyl anthranilate and (-)-Mellein were the most common in each period. The relative amounts of these three chemicals varied with age. [Conclusion]  The secretory activity of the mandibular gland of male C. japonicus is highest in the initial stage of emergence, and gradually decreases with age. Determining the biological function of the chemicals secreted requires further investigation.