The invention discloses brazing filler metal for brazing a W-Cu composite and Fe-based alloy, a method and a brazing technique. The brazing filler metal is in a foil piece strip shape. The thickness of the brazing filler metal ranges from 50 micrometers to 100 micrometers. The brazing filler metal comprises, by weight, 6.0%-9.0% of Mn, 3.5%-5% of Co, 0.3%-1.7% of Ni, 2.0%-5.0% of Zr, 1.2%-2.8% of Ti, and the balance Cu. The brazing temperature of the brazing filler metal ranges from 1000 DEG C to 1050 DEG C, the melting temperature of the brazing filler metal is moderate, and the brazing filler metal is uniformly melted; diffusion and the interface reaction of alloy elements in the brazed connection process can be promoted through a brazing filler metal foil piece, and the wetting and spreading capacity of the brazing filler metal on the surfaces of the W-Cu composite and the Fe-based sintered alloy is improved; crystal particles are refined, residual stress is reduced, and the mechanical performance of joints is improved; the brazing technique for connecting the W-Cu composite and the Fe-based sintered alloy through the brazing filler metal is stable and reliable, vacuum brazed connection is used, a component is in a vacuum state in the heating process, the whole component does not deform, the defects such as microscopic cracks, air holes and inclusions are avoided, and the wetting and spreading capacity of the surface of the brazing filler metal is good.