This study focuses on the application of fly ash (FA)-filled epoxy mortar composite material (EMCM) as a bed material for precision machine tools, emphasizing the impact of fly ash’s primary chemical components (SiO2, Al2O3, Fe2O3, and CaO) as mono-component or two-component fillers on the mechanical properties of EMCM composite material. The research thoroughly analyzed the porosity, macroscopic mechanical properties, and microstructure of the EMCM. The results revealed that increasing the filler content up to 40% significantly enhances the elastic modulus and compressive strength of the EMCM specimens, despite an increase in porosity. Specific filler combinations, such as SiO2/CaO and CaO/Fe2O3, exhibit superior performance. Additionally, Fe2O3 helps prevent sedimentation, enhancing the material’s uniformity. A comprehensive performance evaluation using the Entropy Weighted Technique for Order Preference by Similarity to Ideal Solution (EW-TOPSIS) method showed that specimens containing CaO/Fe2O3 exhibited optimal performance, even when considering cost factors.