By analyzing the shape, pronunciation and meaning of“ ” ,“ ” ,“ ”, this paper finds“ ”is the variant form of yin; In the sutras,“ ” is the variant form of“di” and the pronunciation of“di”or“dai” is different from“ ” in that its meaning is the footprint;“ ” reads“ning”, its meaning is the“peaceful”,“sky”,“large” or“light”. In the sutras,“ ” is the pronunciation of“ming” and it is the vari-ant form of“ming”,with the meaning of“darkness”. Through the research on the three difficult vulgar char-acters, this paper helps the correct interpretation of Buddhist scriptures and points out that the original meaning of“” and“ ” is“peaceful” which is not included in different dictionaries, and thus discusses a kind of existing idea about“”.