Abstract: The effect of Cu-P modification on the microstructure of Al-Si-Zn filler metal and 6061 aluminum brazed joints were investigated.Experimental results showed that the tensile strength of 6061 aluminum brazed joints were improved by Cu-P addition,and the highest value was achieved at 144 MPa when the content of Cu-P was 1.5%.A small amount of P addition can modify the primary Si and refine α-Al in the filler metal.Primary Si growth based on the finely AlP phases were induced by Cu-P addition,and the size of primary Si was much smaller than that without P.Meanwhile,after P addition,the eutectic point of Al-Si moves to the Si side.It can be found that the phases in Al-Si-Zn brazed 6061 aluminum joint are α-Al,η-Zn,and Si particles,and the phases in Al-Si-Zn-Cu-P brazed seam are α-Al,η-Zn,fine Si particles,AlP phase.