Seismic excitation serves as a crucial trigger for slope collapse in seismically active regions. This study employs the nonlinear shear strength reduction (SSR) technique in conjunction with the pseudo-static (PS) method to analyze the seismic stability of 3D rock slopes following the generalized Hoek-Brown (GHB) criterion. Considering the nonlinear characteristics of the GHB envelope, the instantaneous MC parameters for rock masses are identified by locating the tangent at the intersection of the GHB envelope with the shear and normal stress plane. These parameters are subsequently incorporated into the nonlinear SSR analysis for seismic stability based on the Mohr-Coulomb (MC) criterion. The nonlinear SSR technique is then validated by comparing the calculated factor of safety (FOS) with those from other methods and used to assess the impact of geometric and GHB parameters on the FOS of 3D rock slopes. Finally, a set of seismic stability charts for 3D rock slopes in GHB media has been developed and applied to evaluate the seismic stability of two practical rock slope cases following the GHB failure envelope.