Abstract Ash-related problems may induce serious slagging problems in gasification boilers, especially in the presence of alkali and alkaline earth metals at high concentrations. Suitable additives have shown to be promising in suppressing the slagging characteristics of high-alkali coal. In this study, the results of lab-scale experiments for Zhundong coal were demonstrated, especially in Yihua coal (YHc) here, with six common additives, which are kaolin (A), boehmite (B), corundum (C), quartz (D), raw vermiculite (E) and ripe vermiculite (F), at fractions of 3%, 6%, and 9%. The priority of reactions involving AAEM-based species was investigated by characterizing ash samples and thermodynamic equilibrium calculation by Factsage 7.2. The gasification residue of YHc alone (O) was adopted as the reference sample. All six additives could affect the release and transformation of Na, the capture order from high to low was A, F, E, O, B, D, and C, and the slagging risks of different samples were F, E, D, O, A, B, and C in sequence. Given both the ability of additives to capture alkali/alkaline earth metal-based species and the ATFs of the coal ashes, kaolin was proved as a suitable additive for YHc gasification. Furthermore, 6% (mass ratio) was considered the most reasonable addition ratio.