The multielectrode squeeze ER damper was presented.The mathematic model and dynamic characteristics of the ER damper were investigated based on the BiViscosity plasticity model.Then the output forces of ER damper were simulated in different situations under sinusoidal input. Results show that the damper force is an increasing function of the input amplitude, frequency and potential difference,and it is composed of the viscous damping and electrodamping force.Actually the controllable part is the electrodamping force,which can be adjusted by potential difference.The theoretical analysis can also be utilized for the MR damper.