Abstract:A small amount of alkaline compounds and aluminate compounds were mixed as compound activator to activate the activity of sludge ash. While desulfurization gypsum, slag and fly ash were added in a certain proportion to make a new type of clinker-free cementitious materials. The results show that the basic properties of the cementitious material accord with the index of 32.5 composite cement. Firstly, the mixing range of all materials were selected through trial mixing. Then the orthogonal test design was adopted to analyze the influence of each component’s content change on the strength of cementitious materials, and the preliminary mix ratio was selected. Finally, the optimal ratio was selected based on the physical and mechanical properties of the cementitious materials, and the other properties of the cementitious materials were further studied.