A multi-motor system, including a plurality of ECMs. The ECMs include a main ECM and a plurality of subordinate ECMs. A first temperature detection unit and a second temperature detection unit detect a temperature T1 and a temperature T2 at different positions, respectively; the main ECM automatically selects an operation parameter according to temperature differences between the temperature T1 and the temperature T2. The main ECM informs each subordinate ECM of the temperature T1 and the temperature T2, and each subordinate ECM selects an operation parameter according to the temperature T1 and the temperature T2. In operation, the main ECM informs each subordinate ECM of the temperature T1 and the temperature T2, and each subordinate ECM selects an operation parameter in accordance with the temperature T1 and the temperature T2.