Human guidance is the common claim of all religions; this truth has been formed in Islam around the axis of sirati mustaqi, straight path. The importance and the necessity of understanding the meaning of sirat is equal to human guidance and any misinterpretation that leads it to multiplicity and relativity would be against the Qur'an and the Prophet's revelation. Mulla Sadra, commenting sirat and its whatness in the verses of the holy Quran philosophically, opens a new horizon for minds; He view is found in his: Tafsir al-Quran al-Karim and Asrar al-Ayat wa Anwar al-Bayyinat and in his other works. This article has studied his principles for commenting the truth of sirat at first and then, examines the verses in which he has been analyzing and interpreting this matter, and finally, by summarizing the exegetical material, a definition of sirat and sirati mustaqim has been given that is essentially unique.