Abstract: In order to solidify safely radioactive incineration ash, the alkali-activated cementitious materials were prepared with slag, fly ash，cement and zeolite, with water glass or sodium silicate (sulfate) as the activator. The recommended formulation of solidification matrix is 65%(mass fraction, the same below) slag, 10% fly ash, 20% zeolite, 2% cement, 3% Ca(OH)₂. Adding quantity of water glass is 5%，when addition of 30% radioactive incineration ash, with 0.34~0.35 of the ratio of water and ash，the mechanical property of solidification forms performs well. The leaching rate of U for the cement wastes forms is 6.0×10^-6 cm/d in 35 d, and the long time leaching rate is very low. The results of diffusion coefficient of U in the solidification forms indicate that the retention capability about U of alkali-activated cementitious materials is good. The leaching mechanisms of solidification forms are discussed.