The utility model discloses a power grid voltage abnormality alarm circuit including a power circuit, a sampling circuit, a comparison circuit and an alarm circuit. The power circuit provides a voltage analog signal for the circuit. In the sampling circuit, a DC voltage collected from the power circuit is divided by a resistor R1 and a potentiometer RP1 and then input to the comparison circuit for comparison. The comparison circuit compares a voltage sampled by the sampling circuit with an upper limit reference voltage and a lower limit reference voltage separately to determine abnormal situations of a power grid voltage. The alarm circuit gives different alarm sounds to differentiate abnormal voltage situations. The circuit uses cheap electronic elements such as a three-terminal voltage regulator 7812 and a 555 timer as core elements, so that the circuit cost is successfully controlled. Not many resistor elements are used, and thus the power consumption is low. When overvoltage or undervoltage faults happens to a power grid, a buzzer B1 and a buzzer B2 give different sound alarms about fault types.