Abstract:Based on cultural anthropology, this paper explores the cultural meaning and constructive functions of number “three” in Harry Porter. The result shows that with the help of cultural significance of number“three”,J.K.Rowling sets up the perfect combination of characters, stable and varied plot structure and constructs the living magic world. It seems that the mysterious and lucky number “three”in magical thought brought about the unprecedented success to Rowling. In fact, the mature ,stable, full, estimates nature of number“three”determines the perfection and stability of three-philosophy and triassic structure. While good use of the method of philosophy and literature about dividing into three, three sighing with a singing, brings Rowling to the brilliant achievements of today.