The story of route of wet-rice diffusion to Korean peninsular is so far known only piecemeal. It is however commonly agreed that wet-rice technology may have spread the western coastal area in Korea from the lower and middle reaches of the yangzi river in China and to the Shandong peninsular and Bohai Bay region and was then transmitted overland to the area in Korea. Recently excavated three prehistoric paddy fields in Korea provide crucial evidence that helps to solve many of the important problems associated with technological diffusion. Research on the paddy field system and irrigation technology of prehistoric wet-rice has been so far especially productive in Japanese archaeology. Judging from the fact that the Yayoi wet-rice agricultural technology in Japan was transmitted by the Korean Strait from the southern part of Korea it is assumed that people in both regions may have practiced the same technology in prehistoric time. This paper examines three prehistoric paddy fields system(the Majon-ri site the Kwanchang-ri site and the Mujon-dong site) in relation to those of japanese data. The conclusions are as follows ; First early wet-rice agriculture in korea was limited by the level of technology and the size of labour. Secondly the location of field itself was restricted to the lower land and valley bottom area. Thirdly the layout of channel and field network is not very much different from the modern paddy field system.