【Aim】 The Chinese citrus fly, Bactrocera minax (Enderlein) (Diptera: Tephritidae), is an economic pest seriously damaging citrus fruits. Currently, there is a limited body of research on the growth and development of the testis, ejaculatory pump, and ejaculatory pump endoskeleton. 【Method】 We measured the length and width of the testis, ejaculatory pump, and ejaculatory pump endoskeleton of the male adult B. minax using an optical microscope under constant and room temperature rearing conditions. We established functional models for length, width, and index, comparing the differences in organ development between two rearing conditions. 【Result】In both constant temperature and room temperature rearing, the growth patterns of the testis (length, width, and index), ejaculatory pump, and ejaculatory pump endoskeleton followed a power function growth model with the passage of days. No significant differences exist in testis width, ejaculatory pump endoskeleton width, or the length, width, and index of the ejaculatory pump between male adults reared under constant temperature and room temperature conditions. However, the length (4.00±0.14) mm and index (3.40±0.14) of the testis and the length (1.65±0.03) mm and index (1.84±0.08) of the ejaculatory pump endoskeleton in male adults reared at room temperature were significantly higher than the length (3.75±0.13) mm and index (3.19±0.14) of the testis and the length (1.61±0.03) mm and index (1.77±0.08) of the ejaculatory pump endoskeleton in male adults reared at constant temperature. 【Conclusion】 Variable temperature, specifically room temperature, appears to be more conducive to developing testis and ejaculatory pump endoskeleton in male B. minax than a constant temperature. Using ejaculatory pump length to infer the age of male B. minax can improve the efficiency of artificial reproduction and field control effects, providing a theoretical basis for predicting and preventing B. minax infestations.