The invention relates to 
brazing fluxes used for 
welding, in particular to a 
brazing flux used for melt-
brazing of aluminum 
alloy / stainless steel. The brazing flux is characterized in that the brazing flux is prepared by mixing and 
grinding powder of 
potassium tetrafluoroaluminate+
potassium hexafluoroaluminate (KAlF4+K3AlF6) eutectic, 
potassium fluorosilicate, potassium fluoroborate, aluminum, 
zinc, 
tin and 
copper; the brazing flux comprises, by weight, 40%-60% of potassium tetrafluoroaluminate+potassium hexafluoroaluminate (KAlF4+K3AlF6) eutectic, 0-10% of potassium fluorosilicate (K2SiF6), 0-10% of potassium fluoroborate (KBF4), 10%-30% of aluminum (Al), 0-10% of 
zinc (Zn), 0-10% of 
tin (Sn), and 0-10% of 
copper (Cu); the sum of the weight percents of all the raw materials is 100%. According to the brazing flux, the good 
wetting spreading property of an existing brazing flux is maintained, and meanwhile, the texture of a connector is improved, and forming of brittle 
intermetallic compounds is reduced, so that the 
mechanical property of the connector of melt-brazing is improved, and finally 
dissimilar metal of the aluminum 
alloy and the stainless steel is connected reliably with high quality. The brazing flux further has the advantages that the melt-brazing process is relatively simple; the 
energy consumption and the cost of the raw materials are low; the residual quantity of the brazing flux is small after 
welding; and residues are easy to 
clean up.