Coal gangue from Yixing, Jiangsu was investigated. After calcium was introduced into coal gangue, activated samples were prepared under different high temperatures by adding composite mineralizers. X ray diffraction(XRD) method and infrared absorption spectrometry(IR) method were used to analyze their structure characteristics. Cementitious properties of activated samples were also detected. The research results were listed as follows: Under all activation conditions from 1000℃ to 1100℃, CA is produced in activated samples due to the effect of composite mineralizers. CS, Ca3Al10O18 may exist in low activation conditions, such as under 1000℃ and holding 0.5h or 1.0h. And when it comes to 1050℃ with holding 0.5h, Ca3Al10O18 disappears. CS disappears at 1050℃ with holding 1.0h and at the same time ［Ca4(Al2O4)］3- generates. Different activated samples have different cementitious properties. Activated samples calcined at 1050℃, 0.5h show the greatest influence on cement strength, and its compressive strength of 28d can reach 70.16MPa, with substituting 30% mass of cement.