The utility model discloses an automatic blank rotating device of a porcelain insulator, which is characterized in that a blank of the porcelain insulator is fixed on a base (1), the base (1) drives the blank to rotate by a rotating motor (2), a forming knife (8) on a knife carrier (5) drives a feed mechanism (7) by a feeding motor (6) to vertically contact with the inner surface of the blank downwards, and the inner surface of the blank is repaired and formed. The working procedures of rotating and forming the blank of the porcelain insulator can be automatically finished by the automatic blank rotating device of the porcelain insulator. Compared with the prior art, the automatic blank rotating device of the porcelain insulator has the following advantages that: (1) the degree of automation is high, and the manual operation is not needed; (2) an obtained product has high accuracy and stable quality; (3) various blanks of porcelain insulators can be processed by replacing the forming knife and regulating the technological parameter, and the number of suitable products is large; (4) the fully mechanical operation is realized, and the production efficiency is high; and (5) the manpower and the production time are saved, and the product cost is low.