Abstract: A two-degree-of-freedom model for the coupled galloping of an iced conductor is developed in this paper. Using Routh-Hurwitz criterion, the galloping instability of a quasi-oval iced conductor, which have been tested in a wind tunnel by high frequency balance, is investigated on the basis of the new model. The research indicates that: the polynomial form with order higher than seven is sufficient of describing its aerodynamic force coefficients; the swing of the iced conductor has great influence on its stability, while the narrower range of galloping instability wind directions and higher critical wind velocity are obtained from the model without consideration of swing; structure damping plays significant roles in promoting critical wind velocity. These findings in the present paper provide the general characteristics of galloping instability for an quasi-oval iced conductor.