Abstract: The Ostwald ripening and aggregation of neighboring particles occur simultaneously during liquid phase sintering (LPS). A population balance equation was applied to predict the evolution of particle size distribution in aggregation effect during LPS process, a method based on the Euclidean norm was proposed to determine the steady state of particle size distribution in LPS, and the proposed model was applied to predict the upper limit and change rate of particle size during the transition from transient to steady-state. It is found that the particle size distribution reaches a steady-state after the transient coarsening. The modeling and the experimental data reported in literature show good agreement, demonstrating the reliable quantitative prediction by the present numerical model. The present model was adopted to study the particle aggregation by taking Brownian motion into account during LPS. It is also found that the aggregation obviously retards the transition from transient to steady-state, and may even lead to an unsteady-state particle size distribution.