The invention relates to a parallel power supply system for fault detection and power supply modules thereof. Each power supply module includes a phase-shift full-bridge circuit; the output terminal of the phase-shift full-bridge circuit is connected with a primary side of a main transformer (Tr); and a secondary side of the main transformer (Tr) is connected with a rectifier output circuit. And output terminals of arranging output circuits of all power supply modules are connected in parallel. Besides, a fault detection circuit and a drive circuit are also arranged. The fault detection circuit includes a voltage detection circuit that is used for detecting an output voltage of the phase-shift full-bridge circuit; and the drive circuit is used for changing a feedback resistor of a voltage feedback network. The output control of the voltage detection circuit is connected with the drive circuit. The output voltage detected by the voltage detection circuit is low and is outputted; the feedback network is adjusted and a voltage closed ring is adjusted, so that the output voltage is boosted; and thus the module is started again to boost the voltage, so that the output voltage is balanced. Therefore, the starting of the power supply module is realized.