The invention relates to a physical security circuit, in particular to a physical protection interlocking circuit with the acousto-optic warning function. The interlocking circuit is composed of a power circuit, a signal input circuit, a processing circuit, an interlocking control circuit and an acousto-optic warning circuit, wherein the power circuit is composed of a power interface, a rectifier transformer, a rectification integrated block, a voltage stabilization block and a filtering capacitor; the signal input circuit is composed of an infrared ray transmitting tube, an infrared ray receiving tube, a signal transmission interface, a NAND gate and an isolation diode; the processing circuit is composed of a feedback resistor, a NAND gate b, an isolation resistor and a NAND gate c; the interlocking control circuit is composed of a button switch, a NAND gate c, a driving resistor, a triode a, a clamping diode, a relay and an interlocking interface; the acousto-optic warning circuit is composed of a solid voice circuit, a rate resistor, a rate capacitor, a bias resistor, a triode b, a loudspeaker and a warning light emitting tube. Through the protection interlocking circuit, when people enter a dangerous area to perform operation, accidental start of equipment can be automatically stopped, and an acousto-optic warning can be given out.