This study was based on the breeding process of the Pacific Reef Herons (Egretta sacra) bred in Aewol-eup, Jeju Island, for two years from February 2004 to June 2005. The clutch size of the pacific reef herons was $3.24{pm}0.75$(N=17, range: $2{sim}4$), and the egg-laying was at dawn or night intervals of one to three days. The major diameter of the egg(N=39) was $46.73{pm}1.91mm$, the minor diameter thereof $34.06{pm}0.83mm$, the weight thereof $27.67{pm}3.12g$, and the thickness of the egg shell thereof $0.26{pm}0.03mm$. In relation to the breeding cycles of the Pacific Reef Herons, the nesting or nest repairing was made from February to the end of April each year, the egg laying from the beginning of March to the beginning of May, the hatching from the beginning of April to the middle of May, and the nest departure from the middle of May to the end of July. The supplement brood was started immediately from May to June when the first brood had failed. The incubation period was $28.17{pm}4.12(N=6)$ days, and hatched asynchronously. The fledgling period was $40.00{pm}6.84(N=5)$ days, and bill, wing, tarsus and weight developments of early hatched nestlings were the fastest among the same brood. Compared with other egret species, the egg laying period of the Pacific Reef Heron was faster than that of the Black-crowned Night Heron, Little Egret and Great Egret, but later than that of Grey Heron, in Korea.