A power-on reset (POR) circuit includes an RC circuit; a Schmitt trigger, an inverter, and a first PMOS tube. A power supply voltage charges a capacitor through the RC circuit. When a voltage of the capacitor reaches a first threshold, the Schmitt trigger reverses, a first level is output. The POR circuit includes a discharge circuit used to detect a glitch of the power supply voltage, and output a first signal to an input end of the Schmitt trigger when the glitch is detected. The first signal allows the Schmitt trigger to reverse again to output a second level, so as to turn off the first PMOS tube through the inverting amplifier. When the power supply voltage rises along an oblique line again, the Schmitt trigger reverses, and the first level is output, so as to reset the system where the circuit is.