A method for controlling the rotational speed of a fan of an LED lamp, comprising: presetting a corresponding relationship between a voltage, a current and a temperature for an LED chip in the LED lamp in the controller, as well as presetting a corresponding relationship between the temperature of LED chip and the speed of the fan in the controller, measuring the voltage and current of the LED chip, obtaining the current calculated temperature of the LED chip through the measured voltage and current, and further determining the current desired fan speed through the obtained current calculated temperature, using the controller to control the fan to rotate at the current desired speed, thereby cooling the LED chip. Additionally a corresponding system for controlling the rotational speed of the fan of an LED lamp and an LED lamp including the system.