Alkali activated cementitious materials were prepared using lead-zinc tailings as the main materials and adding the supplementary cementitious materials which consist of slag, steel slag, and fluor gypsum. These raw materials were activated by an alkali activator composed of NaOH and sodium silicate. Through orthogonal test, the effects of the modulus of sodium silicate, the content of sodium silicate, and the mass ratio of tailings to supplementary cementitious materials on the mechanical strength of cementitious materials were discussed, and the optimal ratio of raw materials was obtained. Alkali activated cementitious materials based on thermally activated lead-zinc tailings were prepared using tailings that pretreated at 800 ℃, 1 000 ℃, and 1 200 ℃. X-ray diffraction analysis, Fourier infrared spectrometer analysis and scanning electron microscopic analysis were used to characterize tailings and cementitious materials before and after thermal activation. The results show that when the modulus of sodium silicate is 1.8, the mass ratio of sodium silicate is 0.15, and the mass ratio of tailings to supplementary cementitious is 7∶3, the compressive strength of the cementitious material is the highest. The compressive strength of 28 d reaches 20.68 MPa. Inside alkali activated cementitious material exists a generous three-dimensional network structure formed by C-S-H and silicon aluminum polymer which covers the surface of tailings crystal to form a dense matrix providing strength for cementitious materials. When the thermal activation temperature is 1 000 ℃, the compressive strength of cementitious material is enhanced to the greatest extent and the compressive strength of 28 d reaches 28.05 MPa. The internal structure of thermally activated tailings is looser which is conducive to depolymerization of aluminosilicate under alkaline conditions. Meanwhile, more silicon aluminum polymers instead of C-S-H gels were formed, which responsible for higher compressive strength and early hardening characteristics of cementitious materials. The cementitious materials can immobilize Pb and Zn in the internal structure and substantially reduce the leaching of Pb and Zn in tailings. The application of alkali activated cementitious materials may provide a solution to alleviate the harm of heavy metals in tailings to environment.