The synthesis and microwave dielectric properties of CaSiO 3 nanopowder by sol–gel method have been investigated in this paper. CaSiO 3 nanoparticles with an average grain size of 50–60nm were obtained by calcining the CaO–SiO 2 xerogel that was prepared from Calcium nitrate tetrahydrate (Ca(NO 3 ) 2 ·4H 2 O) and tetraethylortho silicate (TEOS). Calcining the CaO–SiO 2 xerogel at 1150°C, the pseudowollastonite-CaSiO 3 phase was completely formed. However, the main phase is not CaSiO 3 or CaSi 2 O 4 but SiO 2 when calcining the mixture of SiO 2 and CaCO 3 at 1150°C. Comparing with CaO–SiO 2 ceramics prepared by solid-state process, the CaSiO 3 ceramics made from nanopowders calcined at 1000°C achieved more compact structure at the sintering temperature of 1320°C, and then had excellent microwave dielectric properties: ɛ r =6.69, Qf=25398GHz.