Abstract: Gasified coal slag serves as a high-quality raw material for preparing non-sintered ceramsite filter media, where mechanical strength and pore structure are critical determinants of filtration performance. Therefore, it is imperative to elucidate the relationship between strength and pore structure in non-sintered ceramsite. By optimizing the formulation of gasified coal slag, metakaolin, and solid alkali activators to develop a non-sintered ceramsite filter material exhibiting a cylinder compressive strength of 25.72 MPa and a bulk density of 1160 kg/m³. Through comprehensive characterization techniques including X-ray diffraction (XRD), scanning electron microscopy (SEM), and solid-state nuclear magnetic resonance silicon spectroscopy (²⁹Si NMR), the strength formation mechanism was investigated. Results revealed that sodium/calcium aluminosilicate hydrate (N/C-A-S-H) gel constitutes the primary strength-contributing phase. The incorporation of metakaolin elevated the Q⁴(2Al) polymer content in N/C-A-S-H gel from 40.34% to 56.05%, thereby enhancing the crosslinking degree of the aluminosilicate network and densifying the gel structure, which ultimately improved the mechanical properties. Pore-forming agents (hydrogen peroxide and cetyltrimethylammonium bromide) were employed to modulate porosity, combined with mercury intrusion porosimetry, the effect of pore forming agent ratio on the porosity, strength, and density of ceramsite was investigated. It was demonstrated that the porosity could increase from 21.33% to a maximum of 50.60%, accompanied by reductions in cylinder compressive strength (8.86 MPa) and bulk density (816 kg/m³). Further analysis of the pore structure characteristics of non-sintered ceramsite was conducted using Menger sponge and thermodynamic fractal models. It was found that the fractal dimension calculated based on the thermodynamic fractal model had a higher linear correlation with the strength of ceramsite, with fractal dimension values ranging from 2.770 to 2.891. This indicates that pore structure evolution in gasified coal slag-based ceramsite is governed by both geometric configuration and thermodynamic mechanisms, with compressive strength inversely proportional to fractal dimension.