"Classification of knowledge" is one of the most important issues in philosophical epistemology. Considering a comprehensive taxonomy of knowledge is prerequisite to be a scientist; therefore, many philosophers have tried to establish as a classification based on certain philosophical and logical foundations. By the same token, many philosophers in the Islamic ages, especially Allame Tabatabaei, have presented specific classifications according to their philosophical attitudes. This study tries to carry out a detailed analysis of classification of knowledge based on Allame Tabatabaei and an abstract of his principles, by which he argues about subject, method and objectives of various ramifications of knowledge as well as Human faculties of Understanding.