Particle dissolution process refers to the dissolving of one liquid or solid phase into another solvent phase. This process is of vital importance in the engineering material science, and chemical engineering, etc. Here, we develop a phase-field model with diffusion-controlled processes at interfaces for isothermal dissolution of alumina inclusion particles in molten silicates, referred as "slag," with comprehensive compositions applied in process metallurgy. The interfacial energy between solid inclusion particle and molten silicate can vary with different temperatures and chemical compositions. This model is validated using experimental data of high-temperature confocal laser scanning microscopy (HT-CLSM) technique. Moreover, the developed model is applicable to predict the dissolution behavior of solid particle in a realistic size scale. The possibility of the model application is illustrated with studies of different physical parameters that affect particle dissolution behavior. The phase-field simulations show that inclusion morphology influences both the dissolution profile and time, and the influence decreases with the increased temperature. Increasing same amount of Al2O3 component in slag, the increased degrees of the alumina dissolution time in silicates with different V-ratio values, a ratio between the mass percent of CaO and that of SiO2, are almost the same. If the V-ratio of slag is relatively small, an increased MgO component in the silicate will significantly decrease the particle dissolution time. On the contrary, the change in MgO component in the silicate will have a minor effect if the value of V-ratio is quite large. In order to rapidly dissolve the inclusion, basicity index (BI) of molten silicate should be larger than 1.4. A balance between BI and MgO component in slag is suggested to be considered to design or optimize molten silicate (slag) for its application in the refining process of steel manufacturing.