Annual changes of the ovaries of Trichiurus haumela were observed. Specimens were collected monthly from the Dang Hai Sea.From December to February of the neat year, the ovaries of hairtails remains at the stage III and passes through the whole winter. From March to April, the ovary develops into stage IV,meanwhile the Cocytes gradually mature in the ovaries. During spawning season from May to August，all stages of IV，V, VI-III, IV' can be found. In the stage V the oocytes are mainly in phase 5, but also contains the phases 3，2 and 1. After releasing one batch of ovum, the spent ovary is observes to be in stage VI-III; the oocytes are mainly in phase 3 and empty follicles are found，then the ovary develops agian into stage IV'，consequently enters stage V'. If enviro-mental conditions are appropriate another spawn may take place.Evidently the development of ooeytes in the ovary of the fish. is in a successive process and the female seems to be able to spawn twice in one spawning seaosn.The spent ovary undergoes a regressive process from September to November.During the regression of stage IV ovary，at first the oocytes in phase 4 atrophp and absorb subseelUently, then the oocytes in phase 3 degenerate and absorbed. The absor-ption of oocytes in phase 4 was brought about by the phagocytic activity of the follicular cells which have been hypertrophied and penetrated into the oocyte; whilethe absorption of oocytes in phase 3 is fulfiled by the protruding of the inner follicular membrane.In the early stage of ooeytes in phase 3,some nucleolar substance, which is considered to be probably related to the formation of yolk within the oacyte，enters into cytoplasm. In the late stage of vitellogenesis the zone radiate of the oocyte degenerate and vanish. There are two layers of gluey membrane outside the plasm membrane of the matured eggs.