Abstract: The number 7 and the typified numbers with 7 (7 as a multiple or mantissa) are particularly prominent in the Eastern and Western literatures during the Mongolian and Yuan Times. However, there is no practical discussion on this issue. These typified numbers actually have a symbolic meaning. By sorting out the numbers 7, 70 and 17, we can find that in the historical materials such as Secret History of the Mongols and the historical materials of the Il-khanate, these typified numbers mostly present the symbolic meaning of “virtual”, while in the historical records of the Yuan Dynasty, there are more “real” meanings. When the Yuan Dynasty records many practical matters of the political and social life on that day, the “real” meaning of this kind of number is obvious; when this kind of number is used on other occasions, it usually presents a patternized phenomenon, and its “virtual” meaning is more important. If such numbers are encountered in the literatures of the Mongolian and Yuan Times, we should not stick to the “real” meaning, should pay more attention to the “virtual” meaning.