The invention discloses a preparation method of a Ti6Al7Nb titanium alloy fine-grain wire material. The preparation method comprises the steps of selecting a Ti6Al7Nb titanium alloy forging stock with uniform longitudinal and horizontal structures, putting the Ti6Al7Nb titanium alloy forging stock in a box type resistance furnace, carrying out high-temperature heating near a phase transformation point, and rolling the forging block into a drawing blank through adopting a single-fire multi-pass method; then, carrying out tube type resistance furnace passing heating on the obtained drawing blank under the phase transformation point, and carrying out multi-pass heating drawing; and finally, carrying out thermal treatment, straightening and polishing to obtain the Ti6Al7Nb titanium alloy fine-grain wire material. According to the preparation method, the Ti6Al7Nb titanium alloy fine-grain wire material obtained through the method is more uniform compared with horizontal structures obtained through a conventional rolling production technology, the crystal grain is fine, the material reaches A1-A2 level in an ETTC2 rating chart, and the performances meet the standard requirements of Ti6Al7Nb rod and wire materials for surgical implants.