Activation of coal gangue from Yixing was done by the method of addition of calcium during calcination. Structural characteristic and cementitious properties of activated samples were analyzed. And then hydration degree of activated coal gangue cement was studied. The results show that: thermally and chemically added-calcium composite activation method can improve the activity of coal gangue. At 1050°C, more effective silicate minerals may be in activated samples, with which cement system may have a higher degree of hydration. infra-red(IR) spectra shows that large number of new mineral peaks can occur in activated sample, and with extending of hydration age mineral peaks gradually decreases until it disappears.