Crime committed by mafia-style criminal gangs is a new category of crime that introduced by the revised Criminal Law in 1997 in China. Three types of “crimes committed by mafia-style criminal gangs” were mentioned in it, namely, crimes of organizing, leading and participating in the mafia-style criminal gangs, crimes of recruiting members of mafia-style criminal gangs by entering the border of China, and crimes of harboring and conniving the mafia-style criminal gangs. However, the definition of the crime committed by mafia-style criminal gangs has long been a controversy either in practice or in theory research since the operation of revised Criminal Law in 1997, notwithstanding the legislature and the judiciary have published a serials of interpretations and criminal amendments about it shortly after 1997. Due to the particularity of this crime, its concept has never been satisfactorily defined. To avoid confusion, it is important to research intensively about the definition of crimes committed by mafia-style criminal gangs, either for applying laws accurately in judicial practice, or for improving and perfecting relevant legislations in the filed of mafia-style criminal gangs. This article makes a theoretical research and practical analysis on the definition of crimes committed by mafia-style criminal gangs, four aspects of features are discussed: organizational feature; economic feature; behavioral feature and feature of illegal control. Borrowing this way of feature division, further analysis will make on Amendment (VIII) to the Criminal Law of China. It will have significant and realistic meanings on the exact application of laws in judicial practice.