The invention discloses boron-containing ti-based composite powder for 3D printing. The composite powder is prepared from, by mass, 0.5-2% of titanium diboride, 98-99.5% of titanium sponge, and the sum of the mass percentage is 100%. The invention further discloses a preparation method of the boron-containing ti-based composite powder. Due to a rapid solidification method, a boron element is addedinto titanium powder, the solid solubility of the alloy element boron in Ti can be greatly increased, and some boron elements are dissolved into a titanium substrate in an over-saturation mode; according to the prepared boron-containing ti-based composite powder, the grain size of an enhancing phase TiB can precisely controlled from the nanometer scale to the micrometer scale through temperatureor energy density, and therefore the enhancing phase ti-based composite materials of different sizes can be prepared, and the requirement for different mechanical performances is met.