Forsterite (Mg 2SiO 4) possesses a high quality factor ( Q· f) of 270,000 GHz and a low dielectric constant ɛ r of 6.8. However, it shows a relatively large negative temperature coefficient of resonant frequency τ f of −73 ppm/°C. For microwave telecommunication, a τ f of nearly 0 ppm/°C is desirable to keep the frequency stability. In order to improve τ f, we have tried to produce pure Mg 2SiO 4–TiO 2 composite ceramics with no secondary phases using a liquid phase deposition (LPD) method. Porous Mg 2SiO 4 ceramics was prepared by sintering Mg 2SiO 4 with polymethyl methacrylate (PMMA) particles, and then TiO 2 was filled in the pores of Mg 2SiO 4 by the LPD method. The porosity and microstructure of porous Mg 2SiO 4 was controlled by amount and particle sizes of PMMA and formation process. τ f of Mg 2SiO 4 filled with TiO 2 by LPD method was improved to −46 ppm/°C.