Abstract: Aiming at the large size and high loss issue of the millimeter-wave (mm-wave) on-chip filtering circuits, the paper proposes a compact filtering power divider based on the external quality factor and metal-insulator-metal (MIM) capacitors loading technique. Size reduction can be realized by proposing an on-chip resonator using two lumped capacitors and one distributed transmission-line inductor. In addition, a miniaturized circuit topology is realized by using the external quality factor. To improve the output isolation, a high-isolation structure merging the complex impedance and a surface-wave-suppression strip is used. Finally, a two-way equal-power 28 GHz on-chip filtering power divider is designed using GaAs-based integrated passive device (IPD) technology, with a minimum insertion loss of 0.9 dB (excluding the power division), a compact size of 0.7 mm², and output port isolation better than 17 dB.