By considering the chains of narrators of the traditions provided in the well known book of "Osoul Al-Kafi", we observe a long list of the reputable traditionists, who are supposed to be more than 37 persons. In this article they are shortly introduced, in an alphabetical order, according to their nicknames from Ibne Babe wayh to yahya attar.under the name of every traditionist, the number of traditions he has related, his teachers and previous narrators and some other brief information are provided.The traditionists are classified into 2 groups: less active and more active groups.Less active group includes those whom shaikh kolaini has related few traditions. On the other hand, the members of active group are those, from whom shaikh kolaini has related frequent traditions.Ibne Ba bewagh, Abi Bakr Jabbal, Ali bin Mousa, and Hasan Bin khafif are from the first group and Ibne Idris, Hamid Bin ziyad, Mohammad Bin Yahya, and Ali Bin Mohammad al-kolaini are in the second group.