Abstract: Addressing the issue of high-frequency oscillation instability in DC microgrids caused by unreasonable virtual inertia control parameters, a low-pass filter equivalent modeling approach is proposed. This approach establishes a reduced-order model of the DC microgrid and its voltage closed-loop transfer function. From the perspective of ensuring the small-signal stability of the DC microgrid, the concept of a feasible region for virtual inertia parameters is defined in the parameter space, with droop coefficients and low-pass filter control bandwidth as the primary parameters. Based on the zeros and poles obtained from the voltage closed-loop transfer function, a method for solving the feasible region of virtual inertia parameters is proposed. This feasible region provides practical guidance for the design of virtual inertia control parameters in DC microgrids. Finally, a simulation case of a DC microgrid based on a switching model is built using PLECS software. Multiple simulation results have verified the effectiveness of the reduced-order model and the feasible region of virtual inertia control parameters.