A foam insulation material was prepared by a wet foam mixing method with recycled powder and slag as main raw materials. The effects of alkali activator CaCl2·6H2O dosage and the preformed foam on the performance of foam insulation materials were investigated via testing the stabilization time of the foam, the condensing characteristics of the slurry, as well as the compressive strength, dry density, porosity and thermal conductivity of the specimens. The pore structure and reaction mechanism were analyzed by image analysis and X-ray diffraction. The results show that the compressive strength of the specimens firstly increases and then decreases with the increase of alkali exciter, and it reaches the maximum value at 5% of alkali activator, but the dosage of alkali activator has little effect on the porosity and dry density. The addition of CaCl2·6H2O significantly shortens the setting time of the slurry, thus favoring that the slurry and the prefabricated foam reach a better matching state, effectively refine the pores and improve the compressive strength and thermal inertia of the specimens. Different density grades of foam insulation materials can be prepared at different amounts of foam admixture. The pore size distribution becomes wider and the compressive strength and thermal conductivity decrease with the increase of foam admixture. The activity of both slag and recycled powder can be effectively stimulated, which can play a coordinating and complementary role to achieve the effect of synergistic utilization of solid waste.