Abstract: Based on previous theoretical models of cavity nucleation during creepdeformation, a new cavity nucleation model is proposed. The basic idea of this new model is that cavity nucleation during creep deformation depends not only on the stress concentration of piled-up group of dislocations, but also vacancy clustering. From the critical radius of cavity nucleation inferred in this paper, not only Raj's critical radius formula but also Smith's critical stress for cavity nucleation can be obtained. The new cavity nucleation model proposed has a wider application than those proposed before.