The transfer matrix,which represents the dispersive medium's layer,can be rigorously obtained by using Lorentz model and considering boundary conditions. The detailed investigation on polaritons in a symmetric photonic crystal with absorptive type of dispersive medium's layer is presented by adjusting parameters of the dispersive medium's layer. It's found that the absorptive type of dispersive cavity and reinforced dispersive cavity may demonstrate similar properties in normal modes coupling,the homogeneous broadening effect,and the detuning effect. But there exists evident differences in transmitted intensity and frequency shift. Finally,the optical bistability in one-dimensional symmetric photonic crystal both with absorptive type of dispersive medium's layer and with Kerr nonlinear layer is also investigated. It's found that optical bistability threshold of the photonic crystal with dispersive medium layer is a little lower than that of structure without dispersive medium layer.