This paper is devoted to the stability analysis of both the true solution and the numerical approximations for nonlinear systems of neutral delay differential equations(NDDEs) of the general form y′(t)=F(t，y(t)，G(t，y(t-τ-(t))，y′(t-τ-(t)))). We first present a sufficient condition on the stability and asymptotic stability of theoretical solution for the nonlinear systems. This work extends the results recently obtained by A.Bellen et al. for the form y′(t)=F(t，y(t)，G(t，y(t-τ-(t))，y′(t-τ-(t)))). Then numerical stability of Runge-Kutta methods for the systems of neutral delay differential equations is also investigated. Several numerical tests listed at the end of this paper to confirm the above theoretical results.
