The reserve of high ash fusion temperature coal in China is huge, and the content of silicon and aluminum in the ash is high,while the content of basic oxide in some sludge is high. The co-gasification of sludge and high ash fusion temperature coal provides thepossibility of regulating the ash melting characteristics of high ash fusion temperature coal. In this study, the effects of municipal sludge(CS) and pharmaceutical sludge (ZY) on the ash melting characteristics of Jiaozuo coal (JZ) with high ash fusion temperature wereinvestigated. The results show that adding CS ash and ZY ash to JZ ash can reduce ash fusion temperature of JZ and adding ZY ash hasa more significant effect on reducing the ash fusion temperature of JZ. When the CS and ZY ash ratio is 15% and 10%, respectively,the flow temperature of JZ-CS and JZ-ZY mixtures are reduced to below 1 380 ℃ to meet the slag discharge requirements of entrainedflow gasifier CS ash has a high CaO content, and ZY ash has a high Fe2O3 content. With the addition of CS ash, the amount of anorthiteformed by reaction of CaO in CS ash with Al2O3 and SiO2 increases,and its co-melting with quartz results in the increase of liquidphase content and the decrease of ash melting temperature. Under a weak reducing atmosphere, the Fe3+ in JZ-ZY ash is reduced intoFe2+, and iron-bearing minerals such as hercynite increases. Hercynite with low melting point can melt at low temperature, and ironbearing minerals easily form low melting point eutectic with other minerals, which decreases the ash fusion temperature (AFT) of JZ.When the proportion of sludge ash added is the same, compared with JZ-CS ash, JZ-ZY ash has a lower theoretical solid content, low⁃er intensity and quantity of crystal phase diffraction peaks. When the temperature is 1 500 ℃ , the mixed ash with 25% ZY ash reachesthe full liquid state, while the mixed ash with 25% CS ash still contains some mullite. Mole ionic potential α is positive linearly correla⁃ted with the characteristic temperatures of both types of mixed ash. The decrease in α value of JZ-ZY ash is greater, so the melting tem⁃perature of JZ-ZY ash decreases more significantly.