The invention relates to a method for analyzing grid-connected inverter system stability by a modified generalized impedance method. The method for analyzing the grid-connected inverter system stability includes establishing a small-signal model of an inverter under polar coordinates according to a grid-connected inverter system, and then establishing a generalized admittance interface model of the inverter and a generalized admittance interface model of a power grid; using the generalized admittance interface models to obtain modified generalized impedance of the inverter and the power grid; acquiring modified generalized impedance criteria from a ratio of the modified generalized impedance of the inverter to the modified generalized impedance of the power grid so as to be used for system stability analysis. The method for analyzing the grid-connected inverter system stability can be used for grid-connected inverter stability analysis with voltage feed-forward filtering reckoned in, is capable of better solving the coupling problem as compared with a general impedance method and can be used for accurately analyzing stability of large-scale grid-connected problems.