This study was conducted to determine the optimum time and the insemination site of frozen in Cheju native cows, and 660 cows first service inseminated with rectovaginal methods by 3 skillful technicians as 3 districts near Cheju City and Sogwipo City areas obtained the following results. Optimum time for insemination was 16-20 hours after the onset of estrus and 80.6% of 67 conceived to first insemination. In the rectovaginal technique used widely at present conception rate for the palpation of ovaries showed 6.6% (index) higher than that of non-palpation. Conception rate of the insemination site; the intra-uterine horn, intra-uterus, just inside the cervix and depositing in mid-cervix were 62.5, 78.4, 74.6, and 80.9% respectively, however, there was no difference in conception rate between cervical and uterine deposition of forzon semen except for the intra-uterine horn.