Abstract： In Sisheng Xinyuan， the masterpieces of the former great Chinese medicine practitioners are referred； the profound mystery of the nature and men is studied，and the key to the sequential and reverse transmissions of qi is explained. The key to the theory of "circulation of qi movement in body" recorded in the book lies in the center qi. If the ascending and descending of the center qi are in order，the clear qi and turbid qi go back to their original positions and the qi movement of the spleen，stomach，liver and lung runs in cycle and in order. Then the intestine runs orderly and the anus would be clear. In conclusion，this theory can be a criterion for constipation.