Although al-Ghazali is known as a critic of philosophers, his intellectual approach is full of rational and philosophical argumentations. That is why, some scholars have taken the view that al-Ghazali has had a big contribution to the rationalization of the Islamic culture and especially in transferring Avicenna's thoughts to his successors. He has also used Avicenna's thought foundations in his religious and mystical theorizations. The present article is an attempt to analyze the relationship between the rational knowledge and the heart-knowledge based on al-Ghazali’s rational mysticism and the main pillars of the new approaches to his works in the last two decades. Based on these bases, it will be argued that the achievement of the highest level of knowledge, which is associated to the heart in al-Ghazali’s thought, is made possible after rational preliminaries. Even the heart knowledge itself is in principle equal to the perfection of the rational knowledge.