The utility model relates to a line signal power judging circuit, which is characterized in that one end of a resistor R1, a positive electrode of a diode V1, a 2-pin of an operational amplifier N1, and one end of a potentiometer R2 are connected; a negative electrode of the diode V1, a 6-pin of the operational amplifier N1, and a positive electrode of a diode V2 are connected; the other end of a capacitor C1, the other end of the potentiometer R2, a negative electrode of the diode V2, one end of a resistor R3, one end of a capacitor C2, and a 3-pin of a voltage comparator N2 are connected; the other end of the resistor R3, and the other end of the capacitor C2 are grounded; a 6-pin of the voltage comparator N2 and one end of a capacitor C3 are connected; the other end of the capacitor C3 is grounded; and a 3-pin of the operational amplifier is grounded. The line signal power judging circuit has the beneficial effects that the circuit can effectively detect whether a signal meets the power requirements or not in the line; the circuit is simple and reliable; the detection circuit is high in sensitivity; and the circuit is practical and flexible, and can set different thresholds.