The invention discloses a preparation method for activating slag micro-powder by titanate, specifically to an activation reaction of slag micro-powder generated by high temperature water quenching and grinding by means of a titanate coupling agent. The titanate coupling agent is dissolved in ethanol containing 1-5% of deionized water so that the solution infiltrates slag micro-powder adequately to hydrolyze the titanate coupling agent in the solution at a certain temperature and normal pressure and be reacted with slag micro-powder. After the solvent is volatilized, active slag micro-powder with organic activity can be obtained. In the activation reaction, the functional group at one end of the coupling agent molecule is reacted with inorganic molecules on the surface of the slag micro-powder. The invention has simple process and flow in preparing the active slag micro-powder and is suitable for industrialized production.