Abstract: The technology for brazing LY12 Al-alloy at middle temperature is realized by improved KF-CsF-AlF3 flux matching Ag-Al-Cu-Zn filler metal.The τ and σ_b strength values of brazed joints,are about 80% and 70% respectirely as compared with the base metal.A way out of the conclusion is found that heat-treated Al-alloy could not be brazed under normal conditions by the results.