This study was conducted to evaluate various factors on milk yield, genetic potential of milk yield and to estimate the lactation curve in Korean Cattle(Han Woo). Milk was collected from 102 heads of Korean Cattle by milking machine from two teats of cattle twice every week for 180 days during 5 years, while the other two teats were suckled by her calves simultaneously. The amount of milk yield was estimated by doubling the collected milk by machine. Average daily and total milk yield of Korean Cattle during 180 days of milking periods were 3.49 and 627.49㎏, respectively. The milk yield of the 3rd and 4th parity were relatively higher than those of the first and the second parity, but there were no significant changes in milk yield after 5th parity. Milk yield of dam during the first month after calving showed significant differences among the years(p$lt;0.05), while no differences during the rest milking period were observed. No differences in daily and total milk yield between the periods of barn feeding(Oct.∼Apr.) and grazing(May∼Sept.). Daily and total milk yield were not affected by the body weight of dam after calving. Lactation curve was calculated by Wood`s imperfect gamma function. Equation of lactation curve was a typical pattern as y=3.6077N^(0.1323) e^(-0.0073N). The day of peak lactation was estimeated about 18 days after calving and the yield of the day was estimated 4.74 ㎏.