The paper addresses the stability of a hybrid system consisting of grid-forming inverters and grid-following inverters, emphasizing the impact of the ratio of grid-forming inverters. In order to investigate the influence, the study sequentially constructs the topology and control strategy of the hybrid system containing the grid-connected inverter and grid-following inverter, using the harmonic linearization method to derive the sequential impedance model for both types of inverters. Based on the sequence impedance model, a three-port equivalent model of the hybrid system is established, and the judgment of its stability is based on the sequence impedance ratio. The paper then plots Nyquist curves to analyze the impact of a higher proportion of grid-forming inverters on the system's stability. Finally, the hardware-in-the-loop (HIL) results are presented to verify the obtained conclusions. And it is also found that a higher percentage of grid-forming inverters compromises the system's ability to follow higher-level power scheduling commands.