Abstract: The origin of localized coarse grains in forged GH49 alloy blades and some approaches of their prevention are studied in this paper. In authors' opinion, the formation of localized coarse grains is primarily due to critical deformation. The mechanism of the formation of coarse grains after critical deformation is the direct growth of some original grains at the expense of others.The primary driving force of grain growth in the critical deformation zone is the difference of distortion energy between two adjacent grains.In order to eliminate coarse grains after critical deformation it is proposed, on the one hand,to minimize the extent of critical deformation zone through controlled deformation;on the other hand,a short time annealing- treatment should be added shortly after fcrging in order to decrease the difference of distortion energy in the critical deformation zone. Experimental results of the above mentioned measures are satisfactory.