The dynamic stability of meso-scale symmetric perturbation is discussed in terms of two-dimensional fluid-dynamics equations under anelastic approximation,which obtains the criterion of symmetric instability in an adiabatic case.The study indicates that the condition of symmestic perturbation is more rigorous for deep convection than that for shallow one,that the disturbance growth rates experience intermittence in their wavelength-dependent variation in the case of non-adiabatic heating,and that unlike it at mid-upper levels, the heating at mid-lower levels exerts a trigger action to the augment of meso-β perturbation,and causes the perturbation to propagate into a warm sector.