The Kan hexagram and Li hexagram in The Book of Changes match with water and fire in the five elements, and kidney and heart in the five viscera. In The Book of Changes, under the normal circumstances, the Kan hexagram and Li hexagram are complementary to each other, the Kan hexagram is up and the Li hexagram is down, the yin and yang are intercourse and the water and fire are harmonization. In traditional Chinese medicine, the fire in heart descends to warm kidney yang, and the water in kidney ascends to nourish heart yin. Therefore, the heart and kidney are interacted, and yin and yang are balanced. Professor Fu Deyu often treats the heart disease by harmonizing the heart and kidney according to the theory of “Kan zhong man, Li zhong xu”, meanwhile emphasizes the application of Chinese medical classical prescription, which obtains good effects. This article introduces the clinical experience of Professor Fu Deyu in treating the heart disease and two proven cases are presented.