In iron-ore sintering process, primary melts fluidity behavior is an important factor for sinter consolidation. Experiments to study the influence of Al2O3 content on the fluidity of primary melts is carried out. With the analysis of microstructure, the property of pore in primary melts is investigated. Results show that the fluidity index of primary melts decreases with the increase of Al2O3 content. XRD results of water quenched sample ascertain that the increase of Al2O3 content can stabilize SFCA, leading to the decrease of primary melts fluidity property. In addition, the fluidity of primary melts can have an influence on the property of pore. Pore structure in primary melts with high Al2O3 content is associated with irregular shape and it also increases the number of pore with size below 50 μm.