Abstract: In this work, the influences of two industrial fluxes (i.e. limestone and clay) and their composite flux on ash fusion and viscosity temperature characteristics of Shanxi typical high-alumina coals were explored, respectively. The results indicated that flow temperature of coal ash decreased with increasing additive amount of flux. Moreover, limestone exhibited a better flux effect than clay, among which the flux effect of composite flux was more obvious than that of the single fluxes. It was also found that limestone could significantly reduce the t_cv of coal ash slag and clay could promote the slag type transformation towards glassy slag. Compared with single fluxes, composite flux exhibited synergistic effect on both the significant reduction of t_cv and the promotion of slag type transformation. For Shanxi typical high-alumina Liangdu coal, when total amount of composite flux was 4% (2% limestone+2% clay), not only the slag transformed into glassy slag, but also t_cv of the slag decreased 133 and 222 ℃ compared with single flux limestone(2%) and clay (6%), respectively. Minerals analysis results confirmed the fluxing principle of different fluxes. After the addition of composite flux, Shanxi high-alumina coals could meet the requirements of industrial entrained-flow gasifier.