Abstract: This paper proposed an impedance sensitivity analysis method based on the equivalent impedance criterion to intuitively and quantitatively investigate the influences of parameters on converter system's stability for different types of impedance systems. The equivalent forms of traditional impedance criteria for four types of impedance systems were deduced, based on which the sensitivity analysis method is introduced. Taking a typical three-phase grid-connected inverter system as the case system, the specific application of the proposed sensitivity analysis method was presented, in which the dominant parameters that affect the stability have been investigated. Based on the sensitivity analysis, the related parameters were adjusted accordingly to improve system stability. The effectiveness of the proposed method was verified by simulations in PSCAD/EMTDC and experiments in RT-lab.