Abstract: The dynamic stability is studied for isotropic viscoelastic cylindrical shell and symmetrically cross-ply laminated viscoelastic cylindrical shell under constant axial loading. The basic equations are established based on Timoshenko-Mindlin theory, the characteristics equation are derived by Laplace transformation for those two kinds of cylindrical shells with two simply supported ends. The stability condition applied in the calculation of critical loads is determined through Routh-Hurwitz theorem. In the numerical examples, critical loads are reduced due to the relaxation feature of the materials and greater effects of transverse shearable deformation on the critical loads are observed in symmetrically cross-ply laminated viscoelastic cylindrical shell than in isotropic viscoelastic cylindrical shell. The influence of rotary inertia is rather small and can be ignored.