The invention provides a grid-side equivalent impedance modeling method taking a static synchronous series compensator into consideration. The method comprises the steps that the SSSC executes an impedance modeling step; according to the topology characteristics of the SSSC, a control loop of an SSSC small signal control link is subjected to harmonic linearization in a frequency domain, by using alinearized result, current response caused by grid harmonic voltage disturbance in an SSSC running state is obtained, and the SSSC running impedance is obtained through calculation. According to thegrid-side equivalent impedance modeling step taking the SSSC into consideration, a target grid-side impedance model is simplified into an equivalent circuit, the line impedance of the equivalent circuit is obtained, and the line impedance is added to the SSSC running impedance to obtain the grid-side equivalent impedance taking the static synchronous series compensator into consideration. The impedance model built for the running impedance of the SSSC in a grid is very precise, and deviations of an existing traditional grid-side equivalent model are reduced.