A dimmable LED lamp, which receives power from a DC power source to emit light, includes a main body, a DC/DC converter, and a LED module; wherein the main body is hollow, and includes a conductive portion made of a conductive material, wherein the conductive portion is connected to the DC power source; the DC/DC converter is provided in the main body, and is electrically connected to the conductive portion of the main body to receive a power from at least a DC power source; the DC/DC converter converts a voltage of the power provided by the DC power source into a corresponding current; the LED module is provided on the main body, and is electrically connected to the DC/DC converter to emit light with luminance corresponding to the current received from the DC/DC converter.