Abstract: Analysis is made on the complex ac response and charge excitation of a quasi-one dimensional electron system with an interaction potential of finite range.The charge excitation spectrum is given after the charge-spin separation with Coleman's bosenization.The ac conductance is obtained with Kubo's formula.It is shown that the spin and backscattering change the relation of the conductance and charge excitation spectrum with wave vector q.The backscatter ing also results in the difference between the charge excitation resonance and the charge conductance resonance.