With the rapid advancement of computer technology, numerical reactors have steadily emerged as a research hotspot. Multi-physical coupling, as the key technology to realize the numerical reactor, has become an important direction in reactor numerical simulation. During the operation of nuclear re-actors, neutronics, thermal-hydraulics, and material corrosion processes, as well as their coupling characteristics, are the critical factors determining the cladding integrity. According to the intrinsic correlation mechanism of multi-physical parameters in the reactor core, this study integrates neutronic, thermal–hydraulic, and material corrosion models, and develops a multi-physical coupling numerical simulation platform based on the unified framework. In the neutronic model, the power distribution is determined using the neutron diffusion equation. For the thermohydraulic model, the temperature and flow fields are solved by the Computational Fluid Dynamics (CFD) method. In the material corrosion model, the thickness and thermal resistance of corrosion products are evaluated based on the growth and thermal resistance models of oxidation corrosion products on aluminum clad-ding. This platform is built based on the open-source CFD software Open-FOAM and is used to perform a three-dimensional high-resolution study on the multi-physical coupling characteristics of the MTR research reactor. The multi-physical coupling simulation of neutronics, thermal-hydraulics, and material corrosion is carried out under long-life conditions for the MTR, and the multi-physical field distribution results after coupling are obtained. In addition, the transient multi-physical coupling simulation of the MTR under an unprotected loss of flow accident is discussed and analyzed, and the responses and safety performance of this reactor under accident conditions are evaluated.