Abstract: With the proposal and gradual implementation of the "double carbon" goal, the stability of grid-connected inverter, as an important interface element for new energy power generation units to connect to the power network, has become prominent. At present, most of the power grid adopts grid-following inverter. However, there is coupling between grid-following inverter, PLL and power grid in weak current network, which seriously affects the stability of the system. Grid-forming inverter shows stronger adaptability than grid-following inverter in weak current network, but there is less discussion on the state space model of grid-forming inverter at this stage, and the stability analysis of grid-forming inverter based on state space model is not deep enough. To address this gap, firstly, the relevant details of state space modeling of grid-forming inverter were presented in detail, including power control loop, voltage control loop, time delay link and LCL filter link. Secondly, the instability of grid-forming inverter was reproduced, and the participation factor analysis was carried out based on the proposed model to verify the effectiveness of the model. Thirdly, based on the model, the instability caused by the change of main link parameters of grid-forming inverter was analyzed. Finally, an improved IEEE 4-node three-phase balanced power grid system was built in Matlab/Simulink for simulation to further verify the effectiveness and practicability of the model.