Abstract: To address insufficient power supply reliability in urban complex large public buildings during outages and distribution network maintenance, a mobile power supply support system was developed. Research was conducted on system architecture, capacity configuration, rapid power access, coordinated control, and power quality regulation. Results show that the coordinated use of diesel generator trucks, energy storage power vehicles, UPS modules, and ATS fast transfer control enables rapid medium- and low-voltage power access, reduces voltage fluctuations and harmonic distortion, and improves power supply continuity for critical loads. The proposed system provides a reference for mobile power supply support in urban complex large public buildings.