The invention belongs to the field of ring rolling design and discloses a design method for the size of a groove and oblique hole ring rolling blank. The design method is characterized by comprising the following design steps that 1, the rolling ratio lambda is determined; 2, the volume V of a groove and oblique hole ring is calculated; 3, the closed type hole rolling is adopted, the cross section of the designed ring blank is rectangular before rolling, and the axial height H0 of the blank before rolling is equal to the height H of the rolled ring; and 4, other sizes including D0 and d0 of the ring blank with the rectangular cross section are designed according to the principle of the invariable volume during plastic deformation. The design process is reasonable, the size of the blank is accurate, implementation of the casting process is facilitated through the designed blank with the rectangular cross section, production efficiency is improved, and waste of energy and materials is reduced.