Modern Chinese Dictionary, one of the most popular language reference books in Mainland China, has been published in seven editions by the end of 2016. As the most important and comprehensive revision was published in 2012, the 6th edition laid the foundation of the next version. The article makes a comparison between the fourth (supplement edition in 2002), fifth and sixth edition of Modern Chinese Dictionary in the changes of entries, phonetic notations, meanings and styles of standard revision in order to reveal the difficulties of the dictionary compilation. On the other hand, based on the evolution of the theory and practice, Modern Chinese Dictionary still needs to be modified constantly.