This paper considers the asymptotic stability analysis of both exact and numericalsolutions of the following neutral delay differential equation with pantograph delay.{x′(t)+Bx(t)+Cx′(qt)+Dx(qt)=0, t>0,x(0)=x0,where B, C, D ∈ Cd×d, q ∈ (0, 1), and B is regular. After transforming the above equation to non-automatic neutral equation with constant delay, we determine sufficient conditions for the asymptotic stability of the zero solution. Furthermore, we focus on the asymptotic stability behavior of Runge-Kutta method with variable stepsize. It is proved that a Lstable Runge-Kutta method can preserve the above-mentioned stability properties.