The treatment of fluidized bed combustion ash and slag (FBC) and the development of environmentally friendly activator material are the effective way to prevent environmental secondary pollution. An organic ethanolamine TEA-inorganic ethanolamine M-inorganic salt composite activator was developed, and the performance of the material was optimized. And the micromorphology, chemical composition and performance changes of the materials were analyzed by SEM, FTIR, XRD and other characterization methods. The influences of three series of activators, M, TEA-M and TEA-M-inorganic salt on the fluidity ratio and compressive activity index of cement slag were explored. The results show that the grinding effect of TEA improves the particle size. The inorganic activator M can affect the content of Ca(OH)2 participating in hydration reaction. The inorganic salt CaSiO3 may produce more C-S-H in the later stage and provide alkaline condition. The synergistic effect of different materials in the composite activator increases the compressive activity index of cement slag by 29 and 18 percentage points at 7 and 28 d (compared with the blank sample), respectively, while maintaining the fluidity ratio of cement mortar at a high level. This study provides an environmentally friendly activator composite material to promote the green application of FBC.