Complete solid solutions between Mg2SiO4 and LiMgPO4 are confirmed by the XRD results. The phase constitution of 0.5Mg(2)SiO(4)-0.5LiMgPO(4) is found to be dependent on firing temperature. The chemical compatibility between Mg2SiO4 and rutile phase at sintering temperature is modified by incorporating LiMgPO4. The microwave dielectric properties of (1 - y)(0.5Mg(2)SiO(4)-0.5LiMgPO(4))-yTiO(2) (y = 0-0.3) composite ceramics have been investigated. The optimized microwave dielectric properties for 0.35Mg(2)SiO(4)-0.35LiMgPO(4)-0.3TiO(2) ceramics sintered at 1050 degrees C show low dielectric constant (11.4), high-quality factor (31 800 GHz), and low-temperature coefficient of resonant frequency (-4 ppm/degrees C).