Abstract: A synoptic and aerological study on a cold wave in the Far East is made during the period of the break down of the blocking situation over Euroasia and Atlantic. It is found that during this period the hemispherical circulation pattern is markedly changed. It is changed from low index pattern into high index pattern. The onset of the cold wave occured during the period of changes. The source of the arctic air for this cold wave may be traced upstream to the Arctic Ocean to the east of Greenland, Furthermore, the structure of the jet streams over 125°E during the cold wave is analysed. Two distinct jet streams-polar front jet and the subtropical jet-were found.