The Uyghur, a Turkic ethnic group, led a nomadic life in the Mongolian steppe until they moved west in the mid ninth century. Some of them established Tianshan Uyghur kingdom, having Turfan as its center. The kingdom lasted until it was destroyed by the Yuan dynasty in the mid thirteenth century. The Tianshan Uyghur people believed in Manichaeism in the early years. Then, early in the tenth century, they converted to Buddhism and developed Buddhist art by adopting Buddhist iconography and working out for a new trend. Vinayavastu Transformation painting, the subject of this study, is representative of the Uyghur kingdom`s Buddhist art. The theme of these paintings is Pranidhi ``making a vow.`` That is why Albert von Le Coq named it Pranidhi scene and it is still called Pranidhi-Szene and in present days. However, examining fifteen paintings of this theme and the accompanying inscriptions in Bezeklik Cave 20 suggests a different and more suitable name for the painting. In specific, the inscriptions and the paintings are the verses in Bhaisajyavastu and their illustration. In other words, Bhaisajyavastu is the iconographical source of the painting. Therefore, this study proposes that this type of painting should be called Bhaisajyavastu transformation tableau. Moreover, on the central shrine`s right and left walls in Bezeklik Cave 20, there remain the Uyghur offering figures and the inscriptions in the Uyghur language. The inscriptions indicate that the Uyghur donors are Sali family, who sponsored the construction of Bezeklik Cave 20. It seems that Sli family, the influential Uyghur nobility in the Turfan area in the tenth and eleventh centuries, expresses their desire to be reborn as Sakyamuni in the next life through Vinayavastu Transformation Tableaux of Bezeklik Cave 20. Specifically, on both sides of walls and the back wall of the circular corridor, the Uyghurs illustrated the verses in chapter fifteen of Bhaisajyavast, which integrates the notion of the pranidhi and the prophecy. And this gives a reasonable account of the fact that Sali family exhibits their aspiration to attain Buddhahood in fifteen panels. Regarding their iconography and composition, the Bhaisajyavastu transformation tableaux produced in Buddhist cultural area of the Uyghur kingdom show the influence of Gandhara and Kizil grottoes in Kucha. However, their standardized composition and the manner in which the panels are arranged, i.e. four to fifteen panels depending on the size and the structure of the caves, result from the Uyghurs` artistic creativity and their desire for the future life. In addition, the notion of receiving prophecy and attaining Buddhahood, which had been established with the influence of Manichaeism, was spread and developed in Bhaisajyavastu transformation tableaux through Bhaisajyavastu.