The invention discloses a titanium-copper dissimilar metal joint welding method, and belongs to the field of metal material interface welding process. The method includes the steps that middle layer welding flux is added between a titanium material and a copper material, the combining interface between the middle layer welding flux and the titanium material is the interface I, the combining interface between the middle layer welding flux and the copper material is the interface II, and welding heat source focal points are located in the middle layer welding flux; in the welding process, it is ensured that when heat generated by a welding heat source is conducted to the interface I, the temperature generated by the heat is higher than the titanium melting point, when the heat is conducted to the interface II, the temperature generated by the heat is higher that the eutectic temperature of the middle layer welding flux and copper, a non-melting welding flux layer exists between the interface I and the interface II, and the middle layer welding flux is a metal material which generates no intermetallic compound with the titanium material and/or copper material. A titanium-copper intermetallic compound is prevented from being formed by means of the welding method, titanium-niobium and copper-niobium melt-brazed seams can be formed at the same time, the extension strength of the obtained titanium-copper dissimilar metal joint reaches 200-240 MPa, the elongation percentage is 30-40%, and the welding interface does not fracture.