Each of the Islamic Scientists, in the process of Understanding and criticism of Ahadis, has had his own bassis and methodology. The present dissertation has tried to investigate and analyze the foundations and methods of Hadis understanding and criticism in the published works by Allameh shaarani. The study of his works reveals that due to his unique capability in analysis and quotations, sound thinking in analytical sciences, firstly his methodological approach resulted in the separation of basics of understanding and criticism of Hadis from it's methodology. And secondly, he has assumed a textual approach in the criticism of Hadis, so he can be regarded as text – oriented researcher in the area of Hadis. He believes that except in disputable jures predent Hadises needing documentation, in other cases evaluation of Ahadis is possible and necessary through the analysis of text, that is, correlation of form and meaning with religeon and reasoning. By validation of reasioning, shaarani has approached the understanding and criticism of Ahadis. The application of reasoning and it's relevant consequences, is so overused that it can be claimed that his basis and methodology in the research on Hadis are the consequences and outcome of his reasoning approach.