In this paper,the linear stability of symplectic methods for Hamiltonian systems is studied.In particular,three classes of symplectic methods are considered:symplectic Runge-Kutta (SRK) methods,symplectic partitioned Runge-Kutta (SPRK) methods and the composition methods based on SRK or SPRK methods.It is shown that the SRK methods and their compositions preserve the ellipticity of equilibrium points unconditionally,whereas the SPRK methods and their compositions have some restrictions on the time-step.
