Editorial on the Research Topic Multi-physics and multi-scale modeling and simulation methods for nuclear reactor application A nuclear reactor works within an intricate circumstance characterized by complicated multi-physics and multi-scale interactions. Its operation necessitates a comprehensive analysis of the interplay among neutronics, fuel property, thermal and hydraulic engineering, chemical kinetics, and the interconnection among the reactor core and the primary loop. By utilizing high fidelity numerical simulations, taking into account the coupling between diverse physics, and providing formidable numerical simulation tools, achieving security, reliable, and cost-effective operation is attainable. Historically, reduced models were employed to represent certain physics phenomena. However, recent advancements in numerical calculation theory, software development, and the capabilities of HPC have propelled the evolution of reactor computational tools towards a paradigm that embraces multi-physics and high-fidelity simulations.Many research has been conducted by coupling multi-physics and multi-scale codes, such as deterministic/Monte Carlo neutronics codes (