Samples of Ti-6Al-4V used in the test of plane strain fracture toughness (KIC) test is fabricated by laser solid forming (LSF). Primary β grain,with a characteristic of epitaxial growth along the depositional direction,shows an average width of 100-400 μm and length of several centimeters. Within β grains,lathy α needles and fine-weaved dense Widmanstatten α+β laths are observed. KIC≥52.6 MPa·m^1/2 reaches the forging standard. And as same as the tensile property of LSF Ti-6Al-4V sample,KIC property presents remarkable anisotropism which is caused by the microstructure characteristic. Fine-weaved dense Widmanstatten α+β laths owns strong ability in anti-crack-propagation,in result,crack-propagation shows sentivites to β grain boundary. If crack propagation runs the direction perpendicular to β grain boundary,KIC value reaches maximum;if crack propagation runs the direction along β grain boundary,the longer the boundary,the higher the KIC value. It is more easier for crack propagation with a small angle between crack-propagation direction and β grain boundary(0-90°). The bigger angle and smaller β grain both result in difficulties in crack-propagation.