The invention discloses an automatic speed-regulating ECM motor. The ECM motor comprises a motor controller and a motor body. The motor controller comprises a control circuit board. A microprocessor, an IGBT module and a motor operation parameter detection unit are arranged on the control circuit board. The microprocessor is connected with a first temperature detection unit and a second temperature detection unit, wherein the first and second temperature detection units are at different positions outside the ECM motor to detect temperatures T1 and T2 of the different positions outside respectively. If the temperature difference between the temperature T1 and the temperature T2 is smaller than or equal to a set value T0, the microprocessor selects a first-gear speed S1 and controls the motor to run at the first-gear speed S1 constantly; and if the temperature difference between the temperature T1 and the temperature T2 is larger than the set value T0, the microprocessor selects a second-gear speed S2 and controls the motor to run at the second-gear speed S2 constantly.