A method for analyzing debris bed formation based on a multi-resolution multiphase particle algorithm, which uses the least-squares moving particle semi-implicit method with second-order computational accuracy and improves surface tension model and free surface particle identification model. The method also utilizes a particle-based gas-liquid phase transition model and a particle-based liquid-solid phase transition model with multi-resolution features, such that the coolant vaporization and melt solidification processes during the falling process of the melt can be calculated. Moreover, a solid-solid collision model is coupled to calculate the collision and debris bed deformation during the falling process of the debris particles. In this way, the momentum exchange, energy transfer and phase transition between different phases are taken into account, and the computational instability caused by the large physical difference between phases is mitigated. A system for analyzing debris bed formation is further provided.