The microwave dielectric properties of (1-x)Ba(Mg$_{1}$3/Ta$_{2}$3/)O$_3$-xBa(Co$_{1}$3/Nb$_{2}$3)O$_3$(x=0.25~0.5) ceramics depending on the Ba(Co$_{1}$3/Nb$_{2}$3/)O$_3$[BCN] contents and the possibility of application as a microwave dielectric resonator were investigated. The specimens were prepared by he conventional mixed oxide method using there sintering temperature of 1575$^{circ}C$. It was found that Ba(Mg$_{1}$3/Ta$_{2}$3/)O$_3$[BMT] and BCN formed a solid solution with complex perovskite structure. As the mole fraction of BCN increased, dielectric constant increased while temperature coefficient of resonant frequency decreased. The highest value of quality factor, Qxf$_{0}$=138,205GHz, obtained in the sample of 0.9BMT-0.1BCN ceramics. In the range of x$geq$0.4, the dielectric constant was about 30. The 0.55BMT-0.45BCN ceramics showed excellent microwave dielectric properties with $varepsilon$$_{r}$=30.84, Qxf$_{0}$=75,325GHz and $ au$$_{f}$=2.9015ppm/$^{circ}C$.EX>.EX>.