Abstract: Conducted interference is widely regarded as the main source of current noise in Electromagnetic Interference (EMI) testing of high-voltage frequency converters, while EMI filters are considered one of the most effective techniques to suppress such interference. To address the problem that existing high-voltage power supply EMI filters do not cover the conducted interference path at the output side and cannot meet the actual EMI suppression requirements at the output side during Electromagnetic Compatibility (EMC) testing of mining high-voltage frequency converters, a single-phase 10 kV high-voltage power supply EMI filter with a π-type structure was designed based on the output characteristics of high-voltage frequency converters under Sinusoidal Pulse Width Modulation (SPWM). The influence mechanisms of motors and their high-voltage cables on the common mode and differential mode interference of the converters were analyzed, and a model of the conducted interference path of the drive system was constructed. Considering high-frequency harmonic characteristics, insertion loss, leakage current, impedance matching, dielectric withstand safety margin, and structural size constraints, a π-type (CLC) EMI filter was selected as the filtering scheme at the high-voltage power supply output side, and the key components and parameters of the EMI filter were determined. Ceramic capacitors were used, with a capacitance to ground of 20 nF; magnetic core inductors with low-loss magnetic material—amorphous nanocrystalline alloy toroidal cores, with a filter inductance of 20 μH. Power-frequency dielectric withstand, partial discharge, temperature rise, insertion loss, and conducted interference tests were carried out. The results showed that the filter effectively suppressed conducted interference in the 0.15-2 MHz frequency band, with a maximum attenuation of up to 62.3 dB, demonstrating excellent conducted interference suppression capability and thermal stability.