It is common sense that Confucianism has long been the most influential philosophy in China. We may safely say that it has been the main shaper of Chinese culture and national spirit for many centuries. The teachings of the Confucian masters have also widely accepted in Japan, Korea and other neighboring countries in East Asia. Of all the followers of Confucius, Chu Hsi of the Sung Dynasty doubtlessly cut a conspicuous figure. His enthusiastic attitude toward life, his exceptionally strong sense of social responsibility, and his warm personality always kept up the spirit of the Oriental peoples in times of difficulties. The purpose of this paper is to show how the teachings of Chu Hsi were introduced to Japan and Korea before Wang Yang-ming of the Ming Dynasty, and how his philosophy became the prevailing doctrine of many generations in both countries.