Abstract: This specification discloses a safe shutdown device for an uninterruptible power supply (UPS) system, which includes a switch module, a counting module, and a shutdown module. The switch module generates an OFF signal to the central processing unit (CPU) of the UPS. After processing, the OFF signal is converted into a first shutdown signal and output to external equipment so as to shut down the external equipment. At the same moment, the CPU of the UPS sends out a second shutdown signal to the counting module to perform counting and generate counting values. When the counting value reaches a predetermined time value, a third shutdown signal is output to the shutdown module. The shutdown module generates a power supply shutdown signal according to the third shutdown signal so as to shut down the UPS itself.