Inhomogeneous deformation and cracking could easily appear during forging for powder metallurgy (P/M for short) superalloy. OM, SEM and TEM were employed to find the reasons of inhomogeneous deformation. The action of annealing on improving the microstructure and malleability was explored preliminarily. The results indicate that inhomogeneous microscopic deformation caused by grains turn and non-uniform secondary particles can lead to inhomogeneous deformation. Through the multistage annealing before forging, equiaxed fine grain layer appeared in the junction of three grains and made secondary particles disperse, which is attributed to homogeneous deformation of P/M superalloy.