Cylindrical cavity expansion problems in the elastoplastic medium are common in geomechanics, including mining and petroleum engineering. The plastic constitutive model is often used to analyze these problems, which obtains a continuum solution. However, localized deformation caused by softening is generally observed in geomaterials, which leads to introduction of the fracture mechanics-based method as an alternative approach to the problem. In this approach, instead of assuming the existence of a plastic zone surrounding the cavity, a group of evenly distributed shear fractures initiates and propagate from the cavity boundary in the elastic medium. The Mohr-Coulomb criterion is enforced over the shear fractures to establish the relationship between the normal and shear stresses on the fracture surface. The minimum plastic dissipation criterion is adopted to determine the fracture propagation direction. The problem is discretized by the displacement discontinuity method, and then solved numerically by an optimization algorithm. The numerical simulation solution converges to the traditional plastic constitutive model as the number of shear fractures increases, with the convex hull of the fracture tips interpreted as the plastic zone. Additionally, the external loading and radial displacement over the cavity boundary also converge to the solution obtained by the traditional elastoplastic solution. This fracture mechanics-based approach provides us with a novel tool for investigating the softening and localization behavior of the elastoplastic medium.