Uninterruptible power system and power control system thereof

An uninterruptible power system and a power control system thereof are disclosed. The power control system includes the uninterruptible power system and a computer system. The uninterruptible power system supplies power to the computer system and includes an external power adaptor, a battery module, a first switch module, a second switch module, and a switching control module. When external power is input, the external power is transmitted to the computer system via the external power adaptor. When the external power is not input, the first switch. module switches automatically to supply a backup power signal from the battery module to the computer system. When the external power is not input and a control signal is not received from the computer system, the switching control module controls the second switch module to electrically disconnect a connection between the computer system and the battery module.