Abstract: The technological advantages of laser additive manufacturing (LAM) for high performance large critical metallic components are briefly introduced, and the main progresson control of solidification grain morphologiesand post-LAM heat- treatment microstructuresfor the LAMed large critical titanium components in the author's team issummarized.The epitaxial growth from the pool-bottom for columnar grain formation and surface heterogeneous nucleation for equiaxed grain formation are found to be the two dominant solidification mechanisms during the layerwiselaser additive manufacturing process. A completed set of solidification grain morphology control method was established and LAMedlarge titanium components with full columnar grains, full equiaxed grains and columnar/equiaxed mixed grains were produced by active controlling the solidification conditions during LAM process. A new special bi-modal microstructure was discovered during the post-LAM heat treatment process and its solid-state phase transformation theory is established.