A combinatory large deformation model of multidirectional forging and subsequent rolling was proposed for producing high performance aluminum alloy ultra-thick plates.The results show that fine-grain (2～3 μm) structures were obtained when total deformation coefficient λ =32 at 250～350 ℃ under a strain rate of about 0.1 s-1.The development of fine-grained structure can be characterized by the formation of strain-induced high energy dislocation and then transforms into new grain under large deformation at moderate temperature.The very fine secondary particles formed during large deformation play important role in retain the stability of the fine-grained structures.