Due to the input capacitive load characteristics of unmanned aerial vehicle (UAV) onboard electronic equipment, a high inrush current is easily induced during DC power-on transients, leading to reduced stability of the power system and potential system-level electromagnetic compatibility (EMC) issues. To address the demand for suppressing transient inrush currents, this study proposes an innovative pre-charge circuit suppression method based on a systematic analysis of traditional surge suppression schemes. By constructing a controllable pre-charge circuit and optimizing the RC time constant design, precise matching between the charging current and time constant is achieved, significantly reducing implementation costs while ensuring system reliability. Engineering validation demonstrates that this method effectively suppresses the peak inrush current within the rated operational current range and maintains stable power bus voltage. The research provides an engineering-practical solution for ensuring power quality in onboard electronic systems, particularly suitable for UAV platforms with stringent requirements for power supply integrity and electromagnetic compatibility.