This study experimentally investigated the potassium fixation ability and ash fusion characteristics during the gasification of corn stalk coke blended with coal ash in CO2 atmosphere. The ash samples were analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). FactSage was also employed to calculate the components and quantities of solid and liquid phase. The results show that the ratio of potassium retained in the biomass ash decreases with the increase in the gasification temperature. In addition, the retention ratio increases with more coal ash added. The improvement of potassium retention ratio is due to the reaction of potassium with alumina/silica to form the solid/slag phase of the potassium aluminosilicates. On the other hand, the ash fusion temperatures of the blended ash are increased by adding the coal ash, compared with the biomass ash. The study confirms that coal ash is a potential additive for not only fixing potassium, but also increasing the ash fusion temperatures of easy-to-slagging biomass.