This invention provides a device and method for detecting a type of a fan. The device for detecting a type of a fan includes a detector and a voltage controller. The detector is used for detecting and comparing a control voltage with a reference voltage to generate a comparison signal and transmitting the comparison signal to the voltage controller. The voltage controller outputs a variable voltage or a constant voltage to a voltage input terminal of a fan according to the comparison signal. The voltage controller can include an integrator for integrating a modulation signal and outputting the variable voltage.