The influences of different heat treatments on the microstructure of TC17 alloy fabricated by laser solid forming (LSF) are investigated,while the alloy in three states of as-deposited,after relief annealing and aging treatment. The results indicate that the microstructure of as-deposited sample consists of coarse columnar grains which grow epitaxially from the substrate along the deposition direction z. The microstructure within the columnar grain showstypical α+β structure. The original β grains are composed of extremely fine basketweave microstructure. And the α phase has lath morphology,its length and width are 1-3 μm and 0.1-0.2 μm,respectively. After furnace cooling (FC) annealing treatment following 1 h holding at 600 ℃,the length and width of the α lath both increased while the length/width ratio decreased,but no other changes can be observed. The equiaxed α phase will be observed on the β matrix after air cooling (AC) annealing treatment following 4 h holding at 550 ℃. During aging treatment,the α laths coarsen continuously as the aging time increases,whereas their length/width ratio gradually decreases. When the holding time reaches 8 h,most of the α laths are spheroidized,only a few left.