A machine boot up protection structure for parallel power supply equipment provides a determination level to set the parallel power supply equipment in an ON condition. It has a control unit to receive a connection signal output by each of power supply units to compare with the determination level. If the comparison matches, all of the power supply units are activated to the ON condition. If the comparison does not match, all of the power supply units are set to an OFF condition. Thereby when the external power is not completely connected, some of the power supply units do not suffer from overloading and damaging.