The manuscript Dunbo 77 at the Dunhuang Museum，contains five kinds of zen texts in all, including the Tan jing (the Platform Sūtra). This manuscript was listed in the first National Precious Ancient Books list of PRC, and was thought to be written during the Gui-yi-jun period. This paper points out that the fifth text of this manuscript, the annotation of the Boreboluomiduo xin jing（the Prajna Paramita Heart Sūtra）annotated by Shi Jingjue in the Tang Dynasty, was written after the Yuan Dynasty，which differs from the first four texts. This annotation of the Heart Sūtra not only has difference with the first four texts on the scribes，the form and arrangement of lines in calligraphy，the identifiers，but also has some folk characters which rarely seen in the Dunhuang manuscripts in it，such as （薩）、（留）、（數）、（燈）、（還）、（離）、（覺）、（顯）、（盡）、（國）、（寶）. Most of these folk characters were created during the Song Dynasty or even after the Yuan Dynasty. According to the above，the annotation of the Heart Sūtra in Dunbo 77 may not belong to the Mogao Grottoes Collections, and is likely to be added to the manuscript after the Yuan Dynasty, or even in modern times.
