Abstract: Eighteen cases with ovarian epithelial carcinoma proved surgically and pathologicallywere performed by chemotherapy combined with cisplatin,adriamycin and cyclophosphamide(PAC) post-operatively. During preoperation, chemotherapy and follow - up, venous blood was sampled to measureCA125 concentration with radio-immunity therapy- The half life period was calculated by CA125 level be-fore the first and third course of the treatment of chemotherapy and Buller's formula. The results showedthat the speed of CA125 level's decreasing in the early period of chemotherapy was related to the progno-sis. Of 18 patients, ten(56 % ) had the half life period20ds and eight of them recurrence and death,whilethe eight wh0se half life period20ds survived quite well. This suggested CA125 level of the early period ofchemotherapy and serum half life period had earlier and more reliable value. If used clinically,it may help tofind drug resistance or recurrence in time so as to take corresponding treating measures early.