Rice husk, a waste material, is which prepared under controlled temperature of 650°C for 1 hour. From results, 97.10 % pure amorphous nano-silica is extracted by precipitation method. Nano-silica studied by TEM, it reveals that the particle is a spherical shape in the agglomeration form with a diameter of 20-50 nm. For preparation of β-dicalcium silicate, it is successfully synthesized this product by nano-silica extracted from RHA cooperated with microwave technique in term of improved the rate of decomposition of CaCO3. Future work, the authors would investigate the hydration reaction for determine the potential of -C2S prepared from microwave technique comparing the traditional -C2S.