Dicalcium silicate is one of the major ingredients of clinker. Because microwave can help chemical reaction occurs a lower temperature than original from the vibration of the particles. It also saves time, energy and cost. In this research, effects of activation with microwave on properties of dicalcium silicate. By using calcium carbonate and nanosilica, which is extracted from rice husk ash with precipitation method is initial raw materials. Activation 700 watts for 0 1 3 5 minutes and calcined at 900 ℃ for 1 hour. The characteristics of nanosilica by X-ray Diffraction (XRD) and Transmission electron microscope (TEM). Dicalcium silicate was characterized by X-ray Diffraction (XRD), Free lime and Scanning Electron Microscope (SEM).