This paper focuses on a group of Old Tibetan manuscripts from Dunhuang that are currently in the Stein and Pelliot Collections, some of which will be reordered and reunited. These texts were previously believed to concern the offering to the seven Tathāgatas or the texts about the former aspirations of the seven Buddhas. However, as my study shows, they actually pertain to liturgies for the seven Tathāgatas including Bhaiṣajyaguru. Based on earlier studies, this research seeks to establish a stronger connection between “pre-canonical” texts and canonical works in Tibetan and Chinese, and to establish a hitherto unknown link in the chain of the textual transmission of this liturgy. After revealing the structure of the liturgy, it seeks to fill the gap between the Bhaiṣajyaguru-sūtra itself and the religious practices of worshipping the seven Tathāgatas including Bhaiṣajyaguru. These are done through a two-dimensional textual analysis, i.e.: 1) identifying the connection between the Old Tibetan materials and the Tibetan canonical version; and 2) analysing the process of the liturgicalization of the sūtra.