In view of the forging problem for void defects of spherical, radial tubular, axial tubular and tangential tubular voids that may exist in hollow ingots prepared by the traditional pouring process, firstly, based on the characteristics of volume energy rate change for void closure, a new void closure criterion of T function was established by the ratio of volume deformation energy rate to plastic deformation energy rate, then it was integrated to the DEFORM software. On this basis, by means of numerical simulation method, the closure behaviors and critical reduction rate were obtained by analyzing void defects of hollow ingots during the deformation process of fress forging which included upsetting, expanding and drawing with mandrel to verify the validity and accuracy of the T function in predicting void closure. The results show that in the free forging process, the voids perpendicular to the loading compression deformation direction can be closed easily, and the voids parallel to the loading compression deformation direction are the most difficult to close. The expanding and drawing  with mandrel processes with local loading and compression should be adopted in the cogging and compaction of hollow ingots, and the void of equivalent size for Φ10 mm can be completely closed when the compression deformation rate reaches to 40% to achieve the effect of eliminating voids and compacting.