Tertullian has been categorised as a fideist for a long time because of his famous motto "Credo quim absurdum". The phrase contradicts logic and empirical knowledge and is regarded as a paradox. It seems that the phrase implies the conflict between reason and faith. Tertullian's attitude towards the relationship between reason and faith has been the focus of many academic fields. This article gives a brief review on several research approaches to Tertullian, such as psychological analysis, philosophical analysis, theology and theosophy. After that, the author returns to the text of Tertullian and make an analysis of it. This article concludes with some comments on the relation between reason and faith.