The microstructures, phase compositions and microwave dielectric properties of ZnAl 2 O 4 –TiO 2 spinel-based composites have been investigated. It is found that ZnAl 2 O 4 cannot form a solid solution with TiO 2 . As TiO 2 content increases, the ε r and τ f values increase gradually, while the Q·f values degrade by degrees. Under the same amount of TiO 2 content, the ε r and Q·f values increase initially and then decrease slightly with increasing sintering temperature, while the τ f values increase slowly. The optimal microwave dielectric properties are achieved in (1−x)ZnAl 2 O 4 –xTiO 2 (x=0.21) sintered at 1500 °C for 3 h with ε r value of 11.4, Q·f value of 71,810 GHz (at about 6.5 GHz), and τ f value of −0.5 ppm/°C.