As one of the presenting modes, numerals have their own specific qualities of language, culture and signs, which could be taken into consideration for literary studies. Due to its mysterious and sacred qualities and its multi-associations with contemporary chaos theory, the numeral three catches the attention of American writer, Cormac McCarthy. In his south-western novels, the numeral three appears frequently, which not only makes McCarthys fiction mysterious and chaotic with its association with numeral culture but also makes the fiction have the characteristics with connotation and thinking of contemporary chaos theory.