In this paper, we  develop  a new reduced basis (RB) method, named as Single Eigenvalue Acceleration Method (SEAM), for second order parabolic equations with homogeneous Dirichlet boundary conditions. The high-fidelity   numerical method  adopts the backward Euler scheme and  conforming simplicial finite elements  for the temporal and spatial discretizations, respectively.  Under the assumption that the time step size is sufficiently small and time steps   are not very large,  we show that the singular value distribution of the high-fidelity solution matrix $U$ is close to that of a rank one matrix.  We select the eigenfunction associated to the principal eigenvalue of the matrix $U^\top U$   as the basis of    Proper Orthogonal Decomposition (POD) method so as to obtain SEAM and a parallel SEAM. Numerical experiments confirm the efficiency of the new method.