Improper setting of control parameters during low voltage ride-through (LVRT) in photovoltaic (PV) grid-connected systems can easily cause their own disconnection, especially when large-scale PV grid connection exacerbates the degree of power electronics in the power system, which can significantly reduce the transient stability of the system. To improve the transient stability of the system, firstly, based on the operating mode of the PV grid-connected system during voltage drop, vector plots are used to analyze the transient stability characteristics of the system during the duration of the fault. Secondly, the single objective linear programming method is used to describe the absolute stability interval of active current command under transient stability constraints, and based on this interval, the geometric analysis method is used to determine the optimal interval of control parameters of the PV grid-connected system. Finally, simulation analysis is conducted on the actual power grid structure of a certain region in Jiangxi Province to verify the effectiveness of the proposed parameter optimization method in improving the transient stability of the system.