This paper analyses in detail the dynamic stability of thedual-excited synchronous generators with non-damping windings,and sets up theundamental equations and the linearized mathematical model for small distur- bance analysis.By an example with computer results,the paper also compareshe difference of the dynamic stabilities between the single-and dual-excited synchronous machines,which explains that the dual-excited synchronous gene- rators can increase the dynamic stability of machines under certain conditions.