The proper translation of sentences from one language into the other is of utmost importance and, in order to accomplish this, the translator should not merely translate the words directly to the target language. Rather it is necessary to consider the concept of conditional sentences in the source language, then the closest structure that makes the same sense in the target language has to be chosen. This is important in translation of the conditional sentences of the Holy Quran into English, due to some differences in the structure of the two languages and the capacity of the target language, and it requires more precision from the translator. In this research, it has been tried to use the descriptive-analytical method to study the various conditional sentences forms in the Holy Qur'an and their exact equivalence in English. Then the most important mistake positions in translation of the conditional sentences of the Quran into English such as the attention to the time of the verbs, the concept of unrealness and unlikeness, the concept of requirement of if clause for the accomplishment of the main clause etc, is mentioned and eventually the function of five translations Arberry, Rodwell, Pickthal, Yusuf Ali and the Saheeh International is analyzed. One of the results of this research is the expression of specific priciples in the translation of Quranic conditional sentences, which improves the translations, and criticizm of the performance of the five translators in question.