Alkali-activated sediment cementitious material was prepared using Zipingpu reservoir sediment as the main raw material, S95 slag powder as the admixture, and Ca(OH)2 as the activator. The samples were characterized by XRD, TG-DTA, SEM, and other analytical methods to explore the impacts of varying Ca(OH)₂ contents on both the macroscopic and microscopic properties of alkali-activated cementitious materials made from Zipingpu reservoir sediment. The results indicate that as the Ca(OH)₂ content rises, the compressive and flexural strengths of the Zipingpu reservoir sediment cement blocks initially display an upward trend and subsequently a downward trend. When the Ca(OH)2 content is 10%, the compressive and flexural strengths of the cement blocks in 28 days are the highest, which are 27.30 MPa and 5.47 MPa respectively. Microscopic analysis shows that with the increase of Ca(OH)2 content, the content of hydration products in the Zipingpu reservoir sediment cemented block gradually increases, and the cemented block structure becomes denser and denser. However, when the Ca(OH)2 content is 12%, excessive alkali activator causes the skeleton structure of the cemented block to be destroyed and the strength is reduced. The Comprehensive analysis of the mechanical properties and structural composition of cemented blocks with different Ca(OH)2 content shows that the optimal Ca(OH)2 content is 10%.