This study was conducted to investigate the anatomical and physiological structures of ovaries in the imported Holstein of Jeju island, total 108 heads of Holstein were participated in this study and the results are summarized as follow: 1. The average weight of left and right ovary is 4.2g and 4.5g in anestrus heifers, 5.4g and 6.0g in anestrus cows and 7.4g and 8.1g in normal cows, respectively. 2. The size of corpus luteum which was projected on surface of ovary in sterile heifer and normal cow is the largest at 11 to 15 days after the occurrence of estrus with length of 1.29㎝ and then was retrograded. 3. Corpus luteum verum during pregnancy weighs 4.73g in the early stage 4.40g in the mid stage, and 3.13g in the late stage, indicate that the most heavy weight was in three months after pregnancy (5.73g) and then the weight gradually reduced. 4. There was no relationship number and size of follicle on the surface of overay between pregnant-period and parturition, but, number and size of developing follicle increases to up to 6 months after pregnancy.