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The mechanism of nuclear irradiation creep can be developed from three levels: the evolution of microscopic defects, the specific action paths of the two types of creep, and the classical theoretical model.: High-energy neutron irradiation of microscopic core origin will produce a large number of supersaturated point defects (vacancies, self-interstitial atoms) in the material lattice. These defects will further evolve into clusters such as dislocation rings and holes, providing the basis for creep deformation. This is the core premise that is different from ordinary thermal creep. The specific mechanism of action of the two types of creep: radiation-enhanced creep: The point defects generated by irradiation greatly increase the dislocation climbing rate. The originally pinned dislocations can continue to move around obstacles, directly increasing the creep rate. Significant deformation can occur even at temperatures far lower than conventional thermal creep. irradiation induced creep: The stress field will guide the directional diffusion of point defects, and dislocations with different orientations will preferentially absorb vacancies or interstitial atoms, triggering anisotropy of material deformation, and become the dominant deformation mechanism in low-temperature irradiation environments with almost no thermal creep contribution. Classic theoretical models support the mainstream SIPN (stress-induced climb) model and SIPA (stress-induced preferential non-equilibrium) model. They are both based on the non-equilibrium diffusion law of point defects under the stress field and quantitatively explain the physical process of dislocation climb acceleration and creep anisotropy. They are the core theoretical basis for predicting irradiation creep behavior in current engineering.