Abstract: At present, most Solid State Power Controller (SSPC) is controlled by switch, the default form is switch off mode which control the circuit on and off by the input signal after power and bias power supply. This paper designs a type of normally-on intelligent power safety switch by the power supply, which has protection function whithout bias power supply. After bias power working, it can control the switch off and on through the input signal. At the same time, the circuit possesses the switch and protection state by isolated output monitoring. The circuit can be used as an executive switch in intelligent distribution system. It can solve the problem that traditional SSPC cannot ensure the power side always work whithout bias power supply. The circuit is fully compatible with the characteristics of fuses, and reduces the power consumption requirements of the system control section by using pulse control mode.