The aim of this article is to study about exact source of al-Shahid al-Shani's al-Bidaya which is known as the first comprehensive usal al-Hadith book in the Shia. Although it is commonly expressed that al-Shahid al-Shani was affected from usal al-Hadith books written by Sunni scholars, it needs to be determined his exact source and dimension of affection by comparing each of them. This also benefits to understand of al-Shahid al-Shani's contribitutions when he adapted it to Shii tradition. So, his additions, extractions and arrangements shed light on Shii Hadith criticism. Consequently, the fact that Shii usal al-Hadith was affected from Sunni books and some arrangements were made with the intent to apply them for Shii Hadith will clarify how this affects structure of Shit usal al-Hadith in the history and today.