Abstract: For the unstable swelling of metal matrix dispersion fuel element induced by the cracking of metal matrix, the static elastoplastic model of crack surface was established without considering viscoplastic deformation, and this model was verified by the finite element simulation. The primary deformation mode transformed from elastic deformation into plastic deformation after the metal matrix completely yielded. The elastic and plastic deformation models of crack surface were established respectively based on the primary deformation modes of metal matrix. According to the balance between internal stress and bending moment, the critical transformation condition of elastic/plastic deformation was obtained. The calculated results of elastic and plastic deformation models fitted well with the finite element simulation, verifying the availability of the static elastoplastic model of metal matrix dispersion fuel under unstable swelling condition.