The invention discloses a brazing filler metal containing lanthanum and neodymium elements for titanium alloy brazing and a preparation method thereof, and belongs to the field of brazing material-high-temperature brazing filler metal. The brazing filler metal is prepared by a base stock consisting of Ti, Cu, Ni and Zr and an adding component consisting of a lanthanum element and a neodymium element through high-temperature smelting. Ti, Cu, Ni and Zr are formed to the base stock by a certain ratio, and rare earths of lanthanum and neodymium are added in the base stock, so that the wettability is improved, the wetting time of a titanium alloy is shortened, and the brazing between the titanium alloys or between the titanium alloy and steel becomes possible; and meanwhile, the hardness and the shearing strength of the brazing filler metal are improved.