S.P.76 is a draft of line drawing from the Library Cave of the Dunhuang Mogao Caves. Author gives a careful study and identifies that two pieces of the painting belongs to the part of draft of illustration of Amitayurdhanasutra seen in the Dunhuang wall-paintings. Then, author investigates the illustration Amitayurdhanasutra in Dunhuang wall-paintings, and finds that a lot of aspects between the draft and the wallpaintings from Mogao Grottoes Cave no.55 are consistent, including the age of the draft and the wall-paining, the contents of the scenes, edition of the Buddhist canon ruled to Paint and layout of drawing structure. The conclusion can be reached that the draft of S. P.76 is the sketch of the illustration of Amitayurdhanasutra in Mogao Grottoes Cave no.55. Meanwhile, it is connected to other paintings of the Mogao Caves with similar themes in same period.