An LED module comprises an LED having an optical axis and a lens for refracting light from the LED. The lens is symmetric relative to a first plane at which the optical axis is located. The peak light intensity in the first plane occurs within 0-5 degrees off the optical axis. The light intensity in the first plane decreases from the peak light intensity with the increase of the angle off the optical axis. In a second plane perpendicularly intersected with the first plane at the optical axis, the peak light intensity occurs within 33-41 degrees off the optical axis, and the light intensity at the optical axis is larger than a half-peak light intensity. Within 0-33 degrees off the optical axis, the light intensity in the second plane increases with the increase of the angle off the optical axis.