A system for testing a power supply unit includes a test sub-system and a test control sub-system connected to the test sub-system and the power supply unit. The test sub-system perform tests and record the results. The test control sub-system is capable of selecting test items to test the power supply unit and setting an execution sequence of the test items. The test items includes a standby test item for testing the power supply unit at a standby state, a normal test item for testing the power supply unit at a normal state, and an over temperature protection test item for testing the power supply unit at an over heated state. The test control sub-system is further capable of automatically switching the standby test item to the normal test item, and switching the normal test item to the over temperature protection test item.