The BaCu(B2O5)（BCB）powder was prepared by solid state reaction under different conditions. And the effect of BCB powder on the microwave dielectric properties of Ba5Nb4O15-BaWO4 (BNBW) ceramics was investigated. The results showed that BCB without secondary phase could be obtained in use of anhydrous ethanol as ball milling medium and being sintered at 800 ℃. Adding a small amount of BCB in BNWB ceramics as a sintering aid can promote the densification of BNBW ceramics effectively sintered at 950 ℃. With the increase of BCB content, the dielectric constant of εr and resonant frequency temperature coefficient of τf decreased monotonously. Meanwhile, the value of Q×f increased firstly and then decreased. When w(BCB) was 1%, BNBW ceramics presented good microwave dielectric properties with εr=19.0, Q×f=33 802 GHz and τf =2.5×10-6/ ℃。