The invention relates to an over-temperature protection circuit. The over-temperature protection circuit comprises at least two temperature detection units, and a protection circuit consisting of series-wound output voltage sources, a voltage-division resistor and multiple shunt-wound voltage-division branches; each voltage-division branch is provided with a switch tube; the junctions of the voltage-division resistor and the voltage-division branches are used for connecting with the voltage output end; each temperature detection unit is correspondingly connected with the switch tube in a driving manner through an isolating element; the temperature threshold values corresponding to the respective temperature detection units are different; and the resistance values of the voltage-division branches corresponding to the respective temperature detection units are different also. The over-temperature protection circuit has two-level or multi-level temperature threshold values, so that stage protection is realized, and the over-temperature protection is more perfect.