We are interested in using the parareal algorithm consisting of two propagators, the fine propagator and the coarse propagator , to solve the linear differential equations u (t)+Au(t) = f with stable impulsive perturbations ∆u(t) = αu(t −) for t = τ l , where α ∈ (−2, 0), ∆u(t) = u(t +) − u(t −), and l ∈. We consider the case that A is a symmetric positive definite matrix and is defined by the implicit Euler method. In this case, provable results show that the algorithm possesses constant convergence factor ρ ≈ 0.3 if α = 0 and is an L-stable numerical method. However, if is not L-stable, such as the widely used Trapezoidal rule, it unfortunately holds that ρ ≈ 1 if λ max >>1, where λ max is the maximal eigenvalue of A. We show that with stable impulses the parareal algorithm possesses constant convergence factors for both the L-stable and A-stable-propagators, such as the implicit Euler method, the Trapezoidal rule and the 4th-order Gauss Runge-Kutta method. Sharp dependence of the convergence factor of the resulting three parareal algorithms on the impulsive parameter α is derived and numerical results are provided to validate the theoretical analysis.