Solid-state sintering is one of the most important material fabrication processes, particularly for materials with high melting temperature. Since the properties of sintered products are significantly affected by their microstructures, it is indispensable to predict and control the microstructure evolutions during sintering. However, experimentally observing the sintering process in situ is almost impossible. Therefore, numerical simulation studies for predicting material microstructural evolution during sintering are crucial. The phase-field method is the most accurate numerical model for predicting material microstructure evolution during sintering [1]. However, phase-field simulations of sintering have been limited to small systems owing to high computational costs. Previous studies [2] have shown that the densification rate significantly depends on the system size. Therefore, it is essential to enable large-scale phase-field simulation for the realistic prediction of microstructure evolution during sintering. In this study, we developed a multi-phase-field sintering model using double-obstacle potential [3], which is effective for large-scale simulation. In addition, to accelerate large-scale simulation, we developed a high-performance computing scheme with multiple graphics processing units. Using this model and scheme, we performed a large-scale sintering simulation with numerous particles. This presentation is based on results obtained from a project, JPNP22005, commissioned by the New Energy and Industrial Technology Development Organization (NEDO). REFERENCES [1] Y.U. Wang, Computer modeling and simulation of solid-state sintering: A phase field approach, Acta Materialia, 54(4):953–961, 2006. [2] M. Seiz, H. Hierl and B. Nestler, An improved grand-potential phase-field model of solid-state sintering for many particles, Modelling and Simulation in Materials Science and Engineering, 31:089601, 2023. [3] I. Steinbach and F. Pezzolla, A generalized field method for multiphase transformations using interface fields, Physica D: Nonlinear Phenomena, 134(4):385-393, 1999.