The effect of laser power on microstructure and properties of Ti-6Al-4V-0.25C alloy was studied by laser melting deposition of Ti-6Al-4V-0.25C prealloy powder containing 0.25wt.%C. The results show that the microstructure of Ti-6Al-4V-0.25C alloy is equiaxed grain morphology, and layered α+β structure is formed inside the grains. The average grain size and α lath size increase gradually with the increase of laser power. In addition, with the increase of laser power, the tensile properties of the alloy are obviously improved, especially the ultimate tensile strength and elongation of the alloy prepared at the laser power of 1500 W are 1191 MPa and 8.3%, respectively. On the one hand, the porosity of the alloy decreases with the increase of laser power. On the other hand, Ti-6Al-4V alloy contains trace element C. During the cooling/solidification process, C atoms are solidly dissolved in Ti matrix, resulting in solid solution strengthening.