The microstructures, tensile strength and fractures of TC4 titanium alloys, fabricated by laser solid forming (LSF), are investigated experimentally in different heat treatment states. The results show that LSF Ti alloy TC4 contains layer bands which stress relief annealing and solid solution aging can help eliminate so that the microstructures become more homogeneous, while the former makes less contribution to the improvement of strength and ductility, the latter can get comprehensive mechanical properties. The tensile fracture shows that the fractures of solution-aging specimens are almost ductile fractures while the as-deposited and stress relief annealing specimens are all mixed fractures. The formation mechanism of cleavage is explained by researching microstructures and fractures which is that cracks propagation along the interface of α/β forms the cleavage plane and the pores joined to the crack forms the dimples.