The invention relates to high-strength high-plastic titanium alloy powder for laser rapid prototyping and repairing, and a preparation method thereof. The powder is prepared from the following components by mass percentage: 5.0-6.2 wt% of Al; 0.25-0.40 wt% of Si; 0.8-2.0 wt% of Zr; 3.5-4.5 wt% of Mo; 0.03-0.08 wt% of O; less than or equal to 0.005 wt% of C, less than or equal to 0.006 wt% of H, less than or equal to 0 .02 wt% of N, less than or equal to 0.05 wt% of Fe, and the balance of a Ti matrix, wherein the sum of the mass percentages of the above components is 100%. The high-strength high-plastic titanium alloy powder improves the plastic reserve of laser melting deposited titanium alloy, and the deposited plasticity and the comprehensive mechanical property are almost the same as those of similar grade forgings, and the severe cracking failure problem, which easily appears, of a large titanium alloy structural member in a continuous long-time laser melting deposition forming process is eliminated, almost no subsequent heat treatment is needed after damaged parts are repaired, and uniform performance of a repaired zone and a base zone can be achieved.