By using equivalent-cavity model, quarter-wave multilayer dielectric mirrors are studied. For the reflection coefficient with the form as ρ(ω)exp[iψ(ω)], it is proved that around the central frequency ω0 of the mirror, ρ(ω) is equal to ρ(ω0) and ψ(ω) is proportional to the frequency ω. And the expressions for the reflectivity reductions and reflection delays of the weakly absorptive quarter-wave multilayer dielectric mirrors are derived. Studies are made on the dependence of the reflectivity reductions and reflection delays on the parity of the layer number. Based upon these studies, A set of weighting factors is extracted, which can be used to quantify the contributions of any individual layer to such important mirror characteristics as reflection reduction, reflection delay, etc.