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The effects of heat treatment on the microstmcture and mechanical properties of laser solid forming (LSF) Ti-6Al-4V alloy were investigated. The influences of the temperature and time of solution treatment and aging treatment were analyzed. The results show that the microstructure of LSFed samples consists of Widmanstatten α laths and a little acicular in columnar prior β grains with an average grain width of 300 which grow epitaxially from the substmte along the deposition direction (Z). Solution treatment had an important effect on the width, aspect ratio, and volume fraction of primary and secondary α laths, and aging treatment mainly affects the aspect ratio and volume fraction of pri-mary α laths and the width and volume fraction of secondary α laths. Globular α phase was first observed in LSFed samples when the sam-ples were heat treated with solution treatment (950℃, 8 h/air cooling (AC)) or with solution treatment (950℃, 1 h/AC) and aging treatment (550℃, above 8 h/AC), respectively. The coarsening and globularization mechanisms of α phase in LSFed Ti-6Al-4V alloy during heat treatment were presented. To obtain good integrated mechanical properties for LSFed Ti-6Al-4V alloys, an optimized heat treatment regimen was suggested.