Abstract: The activity of coal gangue was studied using the combination method of calcination-mechanical grinding in order to investigate the possibility and effects of coal gangue as active mixed materials. The effect of calcination system and grinding fineness on active index of coal gangue were determined according to GB/T 12957-2005“Test method for activity of industrial waste slag used as addition to cement”. Under the optimum conditions of calcination temperature of 800 ℃ for 2h and the specific surface area of 622.2m2/kg, the active index of coal gangue reached to 101.90%, and other indicators ,such as radioactivity, SO3, loss were eligible. It is proved that the active mixed materials of coal gangue, which technical indicators meet the requirements of GB/T 12957-2005, can be prepared using above combination method. The activity of coal gangue is mainly derived from the amorphous minerals transformed from clay minerals and some amorphous silica. The addition of active mixed materials from coal gangue into the cement can increase the output or adjust the mark of cement. The cement mark is not changed and the output is increased when the amount of mixed materials is below 40%. While the amount of mixed materials is between 50%～60%, the output is increased but the cement mark is lowered.

Key words: Key words: coal gangue, calcination, mechanical grinding, active mixed materials, addition amount