The morphology of the second phases formed during the solidification is irregular in many alloy systems, making precise simulation of their dissolved evolution difficult. In this work, a multi-particle spherical log-normal distribution was used to simulate the dissolution of such irregular second phase and took the as-cast Cu-Ti alloy as a case study. The dissolution of the as-cast Cu4Ti phase was simulated via a multi-particle dissolution model integrating the CALPHAD-based diffusion theory (CALPHAD: CALculation of PHAse Diagrams) and high-throughput calculations. The 5041 sub-models (spherical log-normal distributions) replacing the size distribution of the as-cast Cu4Ti phase were initially generated based on the mass balance. Then, data points in 491 sub-models selected from 5041 sub-models were calculated to fit the experimental DSC curves based on the energy conservation, and the best-fitted sub-model could be determined finally. Based on this sub-model, the volumetric and energetic evolution of the as-cast Cu4Ti phase during various dissolution processes could be predicted, and the simulated results were confirmed to be in agreement with the present experimental results. Also, a counterintuitive self-coarsening phenomenon of the Cu4Ti phase has been observed during heating, which has been approved in the experimental work.