The invention discloses a control circuit for detecting alternating current and direct current by a temperature comparison method, which comprises a first thermistor, a second thermistor, a third resistor, a fourth resistor, a first triode, a second triode, a relay and a capacitor; by utilizing the characteristic that the thermistors can change the resistance according to temperature change, the second thermistor is arranged on a circuit board, the first thermistor is lead out by a lead to a conducting wire other conductive bodies to be detected, the second thermistor measures the temperatureof work environment, and the first thermistor measures the temperature around the conducting wire or the other conductive bodies; and when current passes through the conducting wire or the other conductive bodies, heat can be generated, the generated heat causes the resistance of the termistor to change, a detection circuit is triggered to work and the relay is pushed to work so as to realize automatic control. The control circuit has the advantages of simple circuit structure, much low manufacturing cost, high reliability, high sensitivity and adjustability.