MgAl2O4 microwave dielectric ceramics were modified by Zn substitution for Mg, and their dielectric characteristics were evaluated, along with their structures. Dense (Mg1-xZnx)Al2O4 ceramics were obtained by sintering at 1550 degrees-1650 degrees C in air for 3 h, and the (Mg1-xZnx)Al2O4 solid solution was determined in the entire composition range. With Zn substitution for Mg, the dielectric constant epsilon of MgAl2O4 just varied from 7.90 to 8.56, while the Q x f value had significantly improved up to a maximal value of 106 000 GHz at x = 1.0. Moreover, the tau(f) of MgAl2O4 ceramics had declined from -73 to -63 ppm/degrees C.