An exemplary device for controlling rotation speed of a computer fan includes an identifying device and a control circuit. The identifying device is configured for identifying the type of the computer fan. The control circuit configured for controlling rotation speed of the computer fan includes an electric switch, an integrated circuit, a first output terminal, and a second output terminal. The electric switch has a first terminal coupled to the identifying device to receive an identifying signal, a second terminal coupled to a super I/O chip to receive a PWM signal. The integrated circuit is configured to convert the PWM signal to an analog voltage signal. The first output terminal is configured to output the PWM signal to a PWM control pin of a fan header. The second output terminal is configured to output the analog voltage signal to a power pin of the fan header.