Abstract: By the secretory action analysis of hypophysis gonadotropic hormone ( GTH ) cell of long snout catfish ( Leiocassis longirostris ) captured in the estuary of Changjiang River, it was verif ied that combinative injection of LRH - A 50ugPkg and DOM 50mgPkg could stimulate the secretion of GTH, induce the maturation and ovulation of oocyte. The results also indicate that there are two kinds of secretory granules in the GTH cell, one granule is bigger with diameter about 1 200- 2 000nm and lower electron-density ; the other one is smaller with diameter about 300- 500nm and higher electron-density. The release of bigger granule ( secretory gloube) was relative to development and maturation of oocyte while the release of smaller granule ( secretory granule ) was relative to ovulation.