Abstract: Observation on the sexual gland of Boleophthalmus pectinirostris was taken. The morphological structures of oocyte and sperm development of Boleophthalmus pectinirostris were observed by means of light and electron microscopy. According to the histological characteristics of ovary of the fish, The results showed that it spawned once in a reproductive season. The ovaries began to develop in March. Most of the ovaries reached stage Ⅳ and stageⅤ respectively from April to June, which was the spawning season period of the fish with highest monthly average of mature coefficient. The highest mature coefficient of an individual reached the value of 11.2%. Spawning behaviour ended in September. In October, the ovary developed into stageⅡand remained in this stage from October to next February. The oocyte development could be divided into six phases of oogenesis, which were oogonia, oocyte with a single layer of follice cells, oocyte with lipid droplets and yolk globules, oocyte filled with yolk globules, oocyte with migratory nucleus and degenerative oocyte. There was only one layer of membrane surrounding the oocyte whose radiate lines began to appear in the early time of phase 4. The zona radiate grew to its thickest in the late time of phase 4. There was only one fertilization orfice cell on the membrane. The spermary began to develop in February. Most of the sperms reached maturation stage in May, The highest mature coefficient of an individual reached the value of 0.70%, exhausted sperms were most exuberant, the peak arose. Mature coefficient fell very obviously from July to next September. Mature coefficient (ranging from 0.08%—0.20%) changed very smally and remained in this stage from November to next February, in thie period, spermary was condition of rest. By the microscope, the spermary appeared to have a lobular-type structure, and the sperm development could be divided into six phases of spermatogenesis, which were spermatogonia period, the proliferation of spermatogonia, the growth and maturity of spermatocytes, the abnormality of spermatid, the maturity of sperm and degenerative sperm. There were many sperms in the lobular cavity in the breeding season. The spermatangium would disappear in that time.