In this study, the effect of variables including ashing temperature (525°C - 625°C), CaO additive (0 - 4 wt) and blending ratio of rice husk blending (0 - 50 wt) for the improvement of fusion slagging index of biomass is investigated. Response surface methodology (RSM) was used to identify influential factor and predict the interaction between process variables and responses. The results demonstrate that the rice husk blending is the most significant variable for the improvement of fusion slagging index of biomass in comparison with CaO additive and ashing temperature. The optimum parameters for obtaining the highest fusion slagging index of 1470°C were obtained at ashing temperature of 575°C, rice husk blending of 50wt and without CaO additive. © 2019 Author(s).