Commentary additions are among the necessary supplies of every translator; because in some cases the literal translation of the Qur'an does not convey the full meaning of the verse and the deep concepts of the divine word are not conveyed to the reader, so the translators are sometimes forced to add additions to the translation text to clarify the meaning and structure of the translated text well. Among the contemporary Persian translations of the Holy Qur'an, in which commentary additions have a special place is the commentary translation of "Ali Mishkini". This research aims to investigate and analyze the types of commentary additions in Mishkini's translation of Surah "Al-Rahman" using the method of critical analysis. Investigations show that although the translator has tried to provide the reader with better communication with the verses of the Word of Revelation by adding commentary, there have been some slips. The types of interpretative additions, with a critical approach, in Mishkini translation, can be found in the fields of referencing the translation of the words of the verse to the following verses, considering the Qur'anic words and propositions exclusive, using the assumptions of experimental sciences in the translation of the verses, stating specific examples of the verses, not paying attention to the rules of the Arabic language, such as the rule of "Taghlib", the use of some esoteric interpretations in the translation of verses, etc.