Abstract: Indonesia coal shows a good gasification reactivity. However,the high Na2 O content in coal ash can induce some serious problems,such as agglomeration,deposition and fouling. SiO2 -Al2 O3 -Na2 O ternary phase diagram was used to study the phase diagram characteristics of Indonesia coal ash. The blending coal was selected and the blending ratio was optimized. Blended coal gasification experiment,with 75% mass percentage of Indonesia coal,was carried out in a 350 t / d circulating fluidized bed industrial gasifier for 168 h. The operation characteristics and gasification per-formance were investigated. The surface morphologies and phase compositions of bottom char and fly ash were investi-gated via scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses,respectively. During the gasifi-cation process,the temperature and pressure drop for the dense phase of gasifier are very stable,and there are no de-forming or melting phenomenon for fly ash and bottom char. Long-term stable operation is achieved by blended coal gasification. The cold gas efficiency is 71. 96% ,the carbon conversion is 86. 90% and the gas heat value is 5. 59 MJ /Nm3 . XRD patterns show that the peak intensity of albite is very weak for fly ash and bottom char,indicating the formed albite is quite few and helpful to inhibit the low temperature eutectic reaction. The ternary phase diagram pre-diction is consistent with the industrial gasification experiment.