Electromechanical-electromagnetic transient hybrid simulation is an effective method to research the stability of interaction between large-scale grid-connected converters and power grid. Due to the wide-band response characteristics of grid-connected converters, the traditional Thevenin interface model which aims at fundamental frequency equivalence is no longer applicable. In this paper, an interface model based on high frequency equivalent impedance are proposed. This model is based on Thevenin equivalent circuit in controlled source form, which can not only reflect the wide-band characteristics of electromechanical-electromagnetic interaction, but also have high simulation accuracy. The effectiveness of the proposed model is verified by a simulation example.