Abstract: Based on mechanical force activation method and theory, the effects of mechanical force on distribution of particle size and pozzolanic reactivity of siderite tailings were studied. The results showed that the tailings were relatively easy to grind, the role of mechanical force was making the tailings particles distribution change significantly and leading to activation of tailings with a certain pozzolanic reactivity. However, the long time will result in the phenomenon that weak reunion was reduced. And the activity of variance analysis results showed that the ball grinding speed and grinding length had a significant impact on the specific surface of the tailings and pozzolanic reactivity, and among them, the influence of ball mill speed was better to the grinding time.