Considering the endothermic process accompanied by the ash melt and the effect of the ash melt on char particle structure, a fusion gasification model for a single char particle is established. Model predictions and experimental data show that the decreasing trend of the porosity caused by the melt and aggregation of ash is well represented in the model. Compared with the predicted results without consideration of ash fusion, the accuracy is improved obviously. Based on the model, the fusion gasification characteristics of the char are investigated. The results show that when particle size is less than 0.4 mm, the fusion gasification process is more sensitive to the effect of the ash fusion. With the particle size increases from 0.4 mm to 1 mm, the char conversion rate increases by about 5% at 1573 K and 1673 K, while the char conversion rate increases by only about 1% at 1773 K. (C) 2019 Elsevier B.V. All rights reserved.