To effectively alleviate the compatibility problem between activator and calcium-enriched additives during preparation, alkali-activated materials were prepared using slag as the main raw material; hydrated lime (Ca(OH)2), gypsum (CaSO4·2H2O), and calcium carbonate (CaCO3) as mineral additives; and NaOH and liquid sodium silicate (LSS) as activators. The effects of mineral additives and activators on mixing flowability and pouring performance, as well as the compatibility between them, were systematically studied. Further, the synergistic enhancement mechanism between the two was analyzed through compressive strength test and the mechanism was elaborated through microscopic analysis. Results show that Ca(OH)2 could significantly improve compressive strength, but led to the reduction in the mixing flowability. CaSO4·2H2O not only caused a sudden drop in compressive strength, but also significantly reduced mixing flowability. However, CaCO3 did not show any influence. Nonetheless, strong alkaline excitation environment established using NaOH is the prerequisite for the progress of alkali-actiavated reaction and formation of polymerization products. With the increase in NaOH content 8 g (1.78%)–20 g (4.44%, Mass ratio to cementitious material), the adverse effects of Ca(OH)2 and CaSO4·2H2O on the mixing flowability gradually weakened and the strengthening effect on compressive strength enhanced. In contrast, reduction of NaOH content accelerated the self-condensation precipitation of LSS, leading to the decline of mixing flowability.